Basic Science and Structure of the Skin Flashcards

Question

25- A 16-year-old female presents with severe scarring, cystic acne. Which of the following immunologic factors are involved in the pathogenesis of acne? A. TRPV channels B. TLR-2 C. MMPs D. IL-2 E. KLK5

Answer 1

Correct choice: B. TLR-2 Explanation: TLR-2 is a key aspect in the pathogenesis of acne. The other options listed are not key parts of the pathogenesis of acne, some are specifically involved in the pathogenesis of rosacea (KLK5, MMPs and TRPV channels).

Answer 2

Correct choice: A. Internal nares Explanation: Apocrine glands are found in the axillae, anogenital region, external ear canal, eyelids, breast, periumbilical region. Apocrine glands produce an oily fluid rich in triglycerides and fatty acids – subsequent colonization by anaerobic bacteria results in body odor. Apocrine sweat glands are androgen-dependent for their development and have an unclear function in humans; primary locations are the axillae, anogenital region, periumbilical region and nipples Apocrine glands, whose apical portion (acrosyringium) drains into terminal hair follicles, continuously secrete a sterile odorless viscous fluid that is rich in precursors of odoriferous substances.

Answer 3

Correct choice: D. Desmocollin 1 Explanation: IgA pemphigus has two types subcorneal pustular dermatosis type which is due to ab to desmocollin 1 and intraepidermal n eutrophilic IgA dermatosis which is due to ab to desmoglein 3 and 1. Sneddon- Wilkinson disease, also known as sub-corneal pustular dermatosis has an unknown etiology. Desmoglein 1 defect is seen in pemphigus foliaceous and staph scalded skin syndrome. Desmoglein 3 defect is seen in pemphigus vulgaris and intraepidermal neutrophilic IgA dermatosis. BPAg1 is seen in paraneoplastic pemphigus and bullous pemphigoid. BPAg2 is seen in bullous pemphigoid, cicatricial mucous membrane pemphigoid and linear IgA disease. IgA pemphigus (or immunoglobulin A pemphigus) is an autoimmune blistering disorder. It is also called intercellular IgA dermatosis among other names. IgA pemphigus has two major subtypes: 1-Subcorneal pustular dermatosis (SPD) type 2- Intraepidermal neutrophilic (IEN) type. The clinical features of IgA pemphigus include blisters, pustules, erythema, erosions and vegetating lesions. The first signs are flaccid vesicles and pustules. The vesicles and pustules rupture to form erosions and crusted plaques. The eruption tends to follow an annular pattern. IgA pemphigus appears to favor the trunk, upper and lower extremities, axillae, and groin. Mucosal involvement is infrequent. The exact cause of IgA pemphigus is unclear. IgA autoantibodies bind to desmogleins or desmocollins, the cells responsible for adhesion between cells. In SPD-type IgA pemphigus, the autoantigen is described as desmocollin 1, one of the desmosomal cadherins, the glycoproteins that maintain the shape of a cell. In at least some cases of IEN-type IgA pemphigus, the autoantigens are desmoglein 1, desmoglein 3, and an unspecified transmembrane protein.

Answer 4

Correct choice: C. Glycine Explanation: Collagen is composed of 3 chains of amino acids combined into a triple helix configuration. It contains Gly-x-y repeats (glycine is always the 3rd residue). Thus, glycine is the most abundant amino acid in collagen. The remaining answer choices are not the most abundant amino acids in collagen.

Answer 5

Correct choice: E. All of the answers are correct The above listed drugs, as well as beta-lactam antibiotics, antifungals such as ketoconazole and griseofulvin, are known to be secreted into eccrine sweat ducts. This feature may explain the development of neutrophilic eccrine hidradenitis and eccrine squamous syringometaplasia in the context of chemotherapy.

Answer 6

Correct choice: E. Zinc Matrix metalloproteinases are required for normal tissue architecture and normal turnover of the extracellular matrix. All of them have zinc at the active site and require octahedral binding of calcium ions to maintain structural integrity.

Answer 7

Correct choice: C. Macrophages Macrophages are the most important cell for wound healing. They secrete TGFs, cytokines, IL-1, TNF, and PDGF. Neutropenic or lymphopenic patients do not have impaired wound healing, whereas macrophage-deficient (quantity or function) patients heal poorly. Neutrophils however are the first cell type to flood the wound during phase I of inflammation (within first 6-8 hours); this movement is facilitated by TGF-beta. Fibroblasts migrate into the wound by stage II (granulation) where they produced glycosaminoglycans and fibronectin.

Answer 8

Correct choice: E. Synostoses Apert Syndrome is an AD syndrome secondary to a mutation in FGFR2. Also known as acrocephlosyndactyly, this condition includes synostoses of the hands, feet, back and skull as well as generalized acne. Mosaicism of this gene causes nevus comedonicus. There is associated cutaneous and ocular hypopigmentation.

Answer 9

Correct choice: C. Type III Collagen Type III collagen is found in the fetal skin. It is also present in the gastrointestinal tract, blood vessels, and the basement membrane. A defect in this collagen results in the Ehlers-Danlos, vascular type.

Answer 10

Correct choice: B. Inner root sheath The inner root sheath stains red because it contains citrulline. The cortex and medulla along with the cuticle make up the hair shaft. The outer root sheath is the most peripheral cellular structure. The glassy vitreous layer is the basement zone equivalent of hair and is the outermost layer.

Answer 11

Correct choice: D. Loricrin Loricrin is the major component of the cornified envelope (CE). The proteins of the CE are synthesized in the spinous and granular layers. The CE is primarily a protein/lipid polymer formed within the differentiating layer of keratinocytes. The CE eventually exists outside of the cornified cells after the granular cell undergoes a programmed destruction (apoptosis). Self-destructing granular cells are called transition cells.

Answer 12

Correct choice: D. IV Type IV, or circumscribed juvenile, accounts for 25% of total PRP cases. The most common type is Type I, classical adult, which accounts for 55% of cases. Types II, III, and V account for less than 10% each.

Answer 13

Correct choice: D. Desmosine and isodesmosine Desmosine and isodesmosine are the typical amino acids of elastic fibers. Elastic fibers are comprised of elastin that is wrapped by fibrillin microfibrils. Elastic fibers form a complex meshwork extending from the lamina densa of the dermo-epidermo junction through the dermis. Elastic fibers return the skin to a normal shape after being stretched.

Answer 14

correct choice: D. Type VII collagen. Anchoring fibrils are found in the sublamina densa and are made up of collagen type VII. This collagen type is mutated in dystrophic epidermolysis bullosa, and targeted in epidermolysis bullosa acquisita and bullous lupus erythematosus.

Answer 15

Correct choice: A. Eye The eye is the most frequent site of extracutaneous juvenile xamthogranuloma. The second most common site of extracutaneous disease is the lungs. Ocular involvement is typically unilateral.

Answer 16

Correct choice: C. Ectoderm . As implied by the root 'ecto', a prefix meaning "outer", the keratinocytes of the epidermis are derived from the ectoderm. The other layers do contribute cell populations that are present in the skin.

Answer 17

Correct choice: B. Stratum granulosum Pilar cysts do not have a granular layer, they do have all the other layers.

Answer 18

Correct choice: E. Buschke-Ollendorf syndrome Cutis laxa results from decreased desmosine and lysyl oxidase and demonstrates fragmentation and loss of elastic fibers. Marfan's sydnrome results from decreased fibrillin I and demonstrates fragmentation of elastic fibers. Pseudoxanthoma elasticum demonstrates increased glycosaminoglycans on elastic fibers and the accumulation of fragmented and calcified elastic fibers. Anetoderma has decreased desmosine and demonstrates loss and fragmentation of elastic fibers. Buschke- Ollendorf syndrome exhibits increased desmosine and an increased amount of thickened elastic fibers.

Answer 19

Correct choice: B. Fibronectin Fibronectin is a key player in wound healing, initially secreted by myofibroblasts. The bed/matrix of fibronectin provides an adherent base for migration into the wound, provides scaffolding for collagen fibrils and mediates wound contraction. Band-6 protein is a constituent of the desmosomes intracellular plaque. Entactin and nidogen are synonyms and are found in the dermal-epidermal junction, binding to laminin 1s alpha chain. Uncein is associated with anchoring filaments.

Answer 20

Correct choice: E. IL-2 Keratinocytes have been shown to secrete all of the above cytokines, except IL-2, IL- 4, and IFN- gamma.

Answer 21

Correct choice: A. Pityrosporum ovale All the above bacteria and fungi are found within sebaceous glands; the Malasssezia spp. and P. ovale are found within the acroinfundibulum, S. epidermidis is found within the midinfundibulum, and Propionibacterium spp. deep within the follicle.

Answer 22

Correct choice: C. Lamina fibroreticularis comprises of anchoring fibrils and the elastic microfibrils Lamina fibroreticularis comprises of anchoring fibrils and the elastic microfibrils. Lamina fibroreticularis lies below lamina densa. Blood vessels don't cross the dermal-epidermal junction to reach the epidermis. Basement membrane contain both: 1)Lamina basale which include a.lamina lucida and b.lamina densa ( which contain collagene IV & other glycoproteins like laminins,fibronectin etc.) 2)Lamina fibroreticularis contain collagen type III and anchoring fibrils (collagen type VII).

Answer 23

Correct choice: A. Paraneoplastic pemphigus Paraneoplastic pemphigus and drug-induced pemphigus demonstrate direct immunofluorescence staining of the intercellular space and the BMZ, in combination. Anti-epiligrin pemphigoid demonstrates BMZ staining (dermal staining on salt-split skin). Pemphigus vegetans, pemphigus foliaceous, and IgA pemphigus all show intercellular space deposition without staining of the BMZ.

Answer 24

Correct choice: C. Profilaggrin and loricrin Keratohyalin granules are found in the stratum granulosum (the granular layer), and contain the proteins profilaggrin and loricrin. Profilaggrin is converted to filaggrin during the transformation of the granular layer to the cornified layer. This is a calcium-dependent process. Loricrin comprises 75% of the cornified envelopeï¿½s mass.

Answer 25

Correct choice: A. Futcher lines Futcher lines are vestigial lines in which the dorsal surface has more melanocytes than ventral surface. Wallace's lines are the well-demarcated lines around the margin of the foot and hand.

Answer 26

Correct choice: C. Palms Sebaceous glands secrete their contents in a holocrine fashion and are primarily under the influence of androgens. They secrete triglycerides, phospholipids, esterified cholesterol, waxes but not free cholesterol. They may be found in association with hair follicles or in some areas of modified skin such as the nipple/areola, labia minora, prepuce, vermilion border, and eyelids.

Answer 27

Correct choice: A. Contain squalene Odland bodies mediate stratum corneum adhesion in conjunction with FILAGGRIN. They discharge their contents into the extracellular space at the junction of the granular and horny layers establish a barrier to water loss. They are first found intracellularly in upper level keratinocytes and contain ceramides not squalene.

Answer 28

Correct choice:C. The presence of pheomelanin Hair color is determined by melanocytes. The melanocytic activity of follicular melanocytes is coupled to anagen ï¿½ hair is only pigmented when it is growing. Pigment is produced in the matrix area of follicle, above the follicular papilla. Eumelanin is the pigment of brown/black hairs, and pheomelanin is the pigment of red/blonde hairs. Intensity of color is proportional to the amount of pigment. The absence of pigment produces white hair, and markedly reduced pigment produces gray hair.

Answer 29

Correct choice: D. Keratins 5 All subtypes of EBS are caused by a defect in keratins 5 & 14 except EBS with muscular dystrophy which is caused by a defect in plectin. An alpha-6-beta-4 integrin defect is seen in junctional epidermolysis bullosa (JEB) with pyloric atresia. CollagenVII defect is seen in EB aquisita (EBA), Bart's syndrome and dominant EB (DEB). Keratin 1 & 10 defects are not seen in any of the EB subtypes.

Answer 30

Correct choice: B. Elastic fibers are 90% elastin wrapped in fibrillin Elastic fibers are responsible for much of the elasticity of the dermis. They are essentially 90% elastin wrapped in fibrillin. They form 4% of the dry weight of the skin. Fibrillin 1 is mutated in Marfan syndrome. Oxytalan fibers run PERPENDICULAR from the DEJ within the superficial papillary dermis. Elaunin fibers run parallell in thin bands within the reticular dermis.

Answer 31

Correct choice: C. Labia minora Eccrine glands are sweat glands enervated by cholinergic sympathetic nerves mediated by acetylcholine. They absent on modified skin which lacks appendages like the vermillion border, nail beds, glans penis, inner aspect of the prepuce and the labia minora.

Answer 32

Correct choice: D. Aluminium Starch, cactus spines, and wood splinters are PAS positive. Silica, talc, zinc, and wood splinters are positive for bifringence on microscopy.

Answer 33

Correct choice: C. The DEJ deposition is granular The DEJ deposition is granular. The DIF is positive in the vast majority of cases. Deposition of IgM and fibrinogen is within cytoid bodies in the superficial dermis. There is no deposition of IgM within the spinous layer of the epidermis.

Answer 34

Correct choice: D. Wax esters As human sebum exits the sebaceous gland, its major constituents are squalene, cholesterol, cholesterol esters, triglycerides, and wax esters. With passage through the hair follicle, triyglycerides in the sebum become hydrolyzed by bacterial enzymes, so that by the time the sebum reaches the skin surface, it contains free fatty acids, mono- and diglycerides in addition to the original components. Human sebum is distinguished by the presence of wax esters and squalene. The lipids of humaninternal organs contain no wax esters and little squalene. The squalene that is produced in internal organs is quickly converted to lanosterol and then to cholesterol, so it does not remain in its original form. Human sebaceous glands do not convert squalene to sterols.

Answer 35

Correct choice: B. Neural crest Melanocytes are derived from neural crest precursors and migrate to the epidermis, hair matrix, retinal pigment epithelium, ear (stria vascularis), leptomeninges, and mucous membranes. The other options listed are incorrect and are not involved with melanocytes.

Answer 36

Correct choice: D. Palms Apocrine glands operate by decapitation secretion and are activated by epinephrine and norepinephrine. They are located in a few distinct areas of the body, which include axillae, anogenital region, Moll’s glands of the eyelids, mammary glands of the breast and the ceruminous glands of the external auditory canal.

Answer 37

Correct choice: B. A cessation of mitotic activity in rapidly dividing hair matrix cells Anagen effluvium results from an outside stimulus – most often an antimetabolite, chemotherapeutic drug – inducing an abrupt cessation of hair matrix cell mitotic activity. This process occurs within days to weeks of the stimulus, and is reversible with cessation of the drug therapy.

Answer 38

Correct choice: A. Postganglionic sympathetic fibers with acetylcholine as the principal neurotransmitter. Eccrine glands are innervated by postganglionic sympathetic fibers with acetylcholine as the principal neurotransmitter. This explains why medications associated with anticholinergic side effects may be associated with hypohidrosis.

Answer 39

Correct choice: D. All of these options are correct A scar has 5% strength at 1 week, 20% at 3 weeks and 70% at 1 year. It will never recover strength to the level of pre-injury.

Answer 40

Correct choice: A. Type XVII collagen The target for GABEB and bullous pemphigoid is type XVII collagen or BPAG2. It is also the target protein in pemphigoid gestationis, CP and linear IgA.

Answer 41

Correct choice: B. CD6 CD6 and CD11c are expressed on all mononuclear phagocytic cells in the dermis. CD3 is a T-cell marker and CD20 is a B-cell marker. CD34 is expressed on mast cells and CD68 on macrophages.

Answer 42

Correct choice: B. Hours Re-epithelialization begins hours after an injury occurs. Keratinocytes from residual epithelial structures leapfrog each other. One to two days after injury, cells at the wound margin proliferate and begin to migrate into the wound.

Answer 43

Correct choice: D. Are found everywhere on the skin except palms and soles Sebaceous glands are found everywhere on the skin except on the palms and soles. They are multilobular, emptying into the sebaceous duct. Most sebaceous glands are associated with hair follicles, but free glands exist, especially on the lip (Fordyce spots), on the nipple/ areola(Montgomeryï¿½s tubercles), Meibomian glands of the eyelids and Tysonï¿½s glands on the genitalia. The size of the sebaceous glands are not related to the size of the associated follicle. The sebaceous gland enlarges at puberty in response to increased androgens.

Answer 44

Correct choice: C. Primarily a UVA filter Urocanic acid a by product of filaggrin degradation and has a peak absorbtion of 345 nm. It serves as a major UVA filter.

Answer 45

Correct choice: A. Collagen IV Collagen IV is the main collagen component of basement membranes. Collagen I is the main collagen of mature dermis, bone and tendon. Collagen III is found in fetal skin, blood vessels and intestines. Tenascin-X is mutated in some forms of Ehlers- Danlos syndrome and is not associated with the basement membrane. Collagen VII makes up anchoring fibrils and amnion.

Answer 46

Correct choice: A. heparan sulfate proteoglycan All of the listed proteins are present in the lamina densa except alpha-6-beta-4 integrin, which connects the hemidesmosome to laminin 5 in the lamina lucida. The heparin sulfate proteoglycans (perlecan) are negatively charged, thus serve as a permeability barrier. The other listed proteins do not serve this function in the lamina densa. Collagen IV is the main basic basement membrane scaffold. Defects in Collagen IV have been linked to Alportï¿½s and Goodpastureï¿½s syndrome. Nidogen has a ï¿½dumbbellï¿½ shape and binds both laminins and collagen IV in the lamina densa.

Answer 47

Correct choice: D. Calcium The desmosomal connections in the epidermis are calcium dependent. The other options are not required for these connections.

Answer 48

Correct choice: C. Run parallel in bands within the reticular dermis Eulanin fibers are elastic fibers that have less elastin and more fibrillin and run parallel in thin bands within the reticular dermis. Oxytalin fibers contain no elastin and run perpendicular from the dermo-epidermal junction withinthe superficial papillary dermis. Elastic fibers turn over slowly in the skin, and are damaged by ultraviolet radiation.

Answer 49

Correct choice: C. Sebaceous glands found on the eyelids Sebaceous glands enlarge at puberty in response to increased levels of androgens. They are holocrine glands. Meibomian glands are modified sebaceous glands foundin the eyelids. Free sebaceous glands not associated with hairs are found in the nipple and areola and are called Montgomeryï¿½s tubercles. Fordyceï¿½s condition involves free sebaceous glands on the vermillion border of the lips and on the buccal mucosa. Sebaceous glands are found everywhere on the skin except the palms and soles.

Answer 50

Correct choice: E. The melanosomes are positioned after the Golgi apparatus in the secretory pathway. Melanosomes are organelles related to lysosomes and are positioned after the Golgi apparatus in the secretory pathway. Elliptical melanosomes have concentric lamellae and synthesize brown-black eumelanin. Spheroid melanosomes have microvesicular structure and synthesize yellow or red pheomelanin.

Answer 51

Correct choice: C. Zeis glands Zeis glands are sebaceous glands associated with eyelashes. Montgomery's tubercles are present on the areola, Tyson's glands on the labia minora and glans, and Fordyce's spots are located on the buccal mucosa.

Answer 52

Correct choice: C. nasal tip This is innervated by the anterior ethmoidal branch of V1. The infraorbital nerve of V2 innervates the nasal ala. The nasopalantine branch of V2 innervates the columella.

Answer 53

Correct choice: B. Copper Tyrosinase is a copper containing enzyme that is responsible for the conversion to tyrosine to DOPA and DOPA to DOPAquinone.

Answer 54

Correct choice: A. Roof In dystrophic EB the signal localizes to the roof of the blister. In junctional EB, the roof has BPAG2 while the floor has type IV collagen.

Answer 55

Correct choice: A. Inhibitor of CTLA-4 Ipilimumab is an antibody to CTLA-4, this interaction causes inhibition of CTLA-4 which normally inhibits T cell co-activation by binding to B7 (which normally binds to CD28).

Answer 56

Correct choice: C. Elastic fibers Desmosine and isodesmosine are typical amino acids found in elastic fibers. They crosslink fibrillin. Anchoring fibrils are composed of collagen VII and collagen fibers and have the most typical amino acids of proline and hydroxyproline. Heparan sulfate do not typically contain these amino acids.

Answer 57

Correct choice: A. Epidermal side The image shown is bullous pemphigoid. On salt split skin DIF exams, deposits are seen on the epidermal side of the split. If dermal deposits are seen, epidermolysis bullosa acquisita or anti- epiligrin pemphigoid are potential diagnoses.

Answer 58

Correct choice: A. Abnormal crosslinking of collagen Excess homocystine leads to abnormal crosslinking of collagen, with only ~1/3 of crosslinking activity compared to normal controls . The other listed findings are not features of homocystinuria, though hypopigmentation can be a feature.

Answer 59

Correct choice: A. Integrin subunit B4 Integrin subunit B4 is the target for both junctional EB with pyloric atresia and ocular CP.

Answer 60

Correct choice: A. Neonatal LE DIF is of no value in the diagnosis of scleroderma, morphea, and neonatal LE. DIF of lichen planus is positive in the vast majority, with granular DEJ deposition and IgM and fibrinogen staining within cytoid bodies in the superficial dermis. In MCTD DIF shows IgG deposits within epidermal cell nuclei, and rarely along the DEJ. In SLE, while serology is more reliable, DIF can show DEJ deposition in the lupus band test. DIF of erythema multiforme shows immunoglobulin within superficial vessel walls, DEJ, and cytoid bodies.

Answer 61

Correct choice: B. Type III collagen Type 1 collagen is the most prevalent collagen in skin, accounting for 80% or more of the total collagen in the adult dermis. Type III collagen is the next most predominant collagen in human dermis, accounting for approximately 10%. Type IV collagen is found in basement membranes. Type VII collagen is found in human dermis as anchoring fibrils. Type XVII collagen, also known as BPAG2, is an important transmembrane pro tein in the basement membrane zone.

Answer 62

Correct choice: B. Fibronectin Granulation tissue forms approximately four days after injury. It is composed of new capillaries, macrophages, fibroblasts, and blood vessels. The formation is dependent on the presence of fibronectin. There tends to be an ordered sequence of matrix deposition. Fibronectin is deposited first followed by collagen 3 and then collagen 1. Granulation tissue primarily contains type 3 collagen.

Answer 63

Correct choice: A. Respond to chemical stimuli such as hormones Sebaceous glands are androgen-responsive holocrine glands that enlarge at puberty. Meibomian glands of the eyelids are modified sebaceous glands. Sebaceous glandsare found everywhere on the skin except the palms and soles. Fordyceï¿½s condition involves free sebaceous glands on the vermillion border of the lips and on the buccal mucosa. Eccrine glands are thermoregulatory structures that respond to cholinergic stimulation.

Answer 64

Correct choice: A. Regulate water-binding capacity The function of glycosaminoglycans/proteoglycans in the dermis is to regulate water-binding capacity. The other listed options are not functions of glycosaminoglycans / proteoglycans.

Answer 65

Correct choice: E. Odland bodies Odland bodies, also known as lamellar granules, keratinosomes, and membrane-coating granules, are small organelles that are discharged from granular cells into the intracellular space of the granular layer of the epidermis. These bodies have two known functions: they mediate stratum corneum cell cohesion and they form a barrier to water loss. Odland bodies are round to oval, measure approximately 300 to 500 nm in diameter, and possess a trilaminar membrane and a laminated interior. They contain neutral sugars linked to lipids and/or proteins, hydrolytic enzymes, and free sterols. Filaggrin is a breakdown product of filaggrin precursor, acomponent of keratohyaline granules, which aggregates with keratin filaments and acts as a "glue" for keratin filaments. Involucrin is a cysteine-rich protein synthesized in the cytoplasm of spinous cells. The enzyme, transglutaminase, cross-links involucrin in the granular layer forming an insoluble cell boundary that is resistant to denaturing and reducing chemicals. Loricrin, is a highly insoluble sulfur- and glycine/serine-rich protein, which is the major protein comprising the cornified cell envelope.

Answer 66

Correct choice: B. Beta-catenin Beta-catenin is the downstream mediator of WNT signaling. Through a series of signals, WNT proteins inhibit the degradation of beta-catenin in the cytoplasm. After being translocated to the nucleus, beta-catenin then forms a complex with LEF/TCF transcription factors, which ultimately results in expression of downstream genes. Activation of this pathway is necessary for epithelium to have the potential to develop a hair follicle.

Answer 67

Correct choice: E. Fordyce's spots Fordyce's spots are located on the buccal mucosa and vermilion border of the lips. Montgomery's tubercles are present on the areola, Tyson's glands on the labia minora and glans, meibomian and Zeis glands are present on the eyelids.

Answer 68

Correct choice: E. Hyponychium The hyponychium is the structure that delineates the anatomic region between the nail bed and the distal groove, where the nail plate detaches of the distal portion of the digit. The corneal layer of the hyponychium accumulates in part under the free margin of the nail plate. In most cases, the hyponychium is covered by the distal nail plate, however, it may become visible in the case of nail biters.

Answer 69

Correct choice: A. S-100 Eccrine glands stain S-100 and CEA positive. The remaining stains would not be expected to stain normal eccrine sweat glands. Prussian blue (Perl’s) is an iron stain which stains iron or hemosiderin bright blue. Giemsa stains mast cell granules purple (heparin in the granules) and can also be useful in staining in Leishmaniasis. Verhoeff von Gieson is a stain for elastic tissue that stains blue-black. Steiner stain is a silver stin for spirochetes similar to a Warthin Starry or Dieterle stain.

Answer 70

Correct choice: A. All the options are correct The hair follicle converts gonadal or aderenal testosterone to dihydrotestosterone locally via 5-alpha reductase. It also cleaves proopiomelanocortin to ACTH, alpha- MSH, and B-endorphin via prohormone convertase. It also secretes corticotropin releasing hormone (CRH) as well as prolactin.

Answer 71

Correct choice: C. Allow rapid shunting of blood from the arterioles to venules, bypassing capillaries. Tumors composed of glomus cells are usually PAINFUL, not asymptomatic. They are derived from Suquet-Hoyer canals and allow rapid shunting of blood from the arterioles to venules. Glomus cells are part of glomus tumors which are most often solitary, purple dermal nodules on the extremities. Most often, they are seen on the fingers and toes. They are usually painful and rarely malignant. As opposed to a glomus tumor, glomangiomas are usually painless. They also most often occur on extremities, but can also occur on the trunk.

Answer 72

Correct choice: C. Susquet-Hoyer canal Glomus cells are vascular smooth muscle cells derived from the arterial portion of the glomus body, or the Sucquet-Hoyer canal, which is an arteriovenous shunt in the dermis that contributes to temperature regulation. Glomus are found primarily on the palms and soles and function to allow the rapid shunting of blood from the arteiolesto venules. Disease processes involving glomus cells include glomus tumor and glomangioma.

Answer 73

Correct choice: C. IL-6 Adipocytes secrete tumor necrosis factor (TNF)ÃŽÂ±, interleukin-6 (IL-6), leptin, adiponectin, angiotensinogen, and resistin. Specifically it has been shown that IL-6 mRNA levels in human subjects are significantly greater in adipose tissue than in other tissues known to express IL-6. It is thought that circulating IL-6 levels may be higher in obese patients, contributing to the development and progression of vascular disease in this patient population.

Answer 74

Correct choice: D. Central depression within a lesion when squeezed along its margins Central depression within a lesion when squeezed is referred to as the dimpling sign and is seen in dermatofibromas. Nikolsky sign can be seen when an intact epidermis shears away from the underlying dermis, leaving a moist surface (seen in pemphigus vulgaris, staphylococcus scalded skin syndrome (SSSS), and toxic epidermal necrosis). Spreading bulla phenomenon with pressure on an intact bulla is referred to as Asboe-Hansen sign, commonly seen with pemphigus vulgaris. Swollen, itchy and or red after stroking the skin is referred to DarierÃ¢Â€Â™s sign and can be seen in systemic mastocytosis or urticaria pigmentosa. Disappearance of color or blanching when the lesion is pressed is commonly found on vascular lesions.

Answer 75

Correct choice: B. 17 Acidic keratins (K9-20) are expressed from chromosome 17. Basic keratins (K1-8) are on chromosome 12. The other listed chromosomes are not involved in keratins.

Answer 76

Correct choice: E. Adrenocorticotropic hormone Both alpha-MSH and ACTH are cleavage products of proopiomelanocortin (POMC).

Answer 77

Correct choice: C. 3 months The average duration of the telogen phase of the hair cycle is 3 months; this feature explains why telogen effluvium is typically observed 3 months following a traumatic event or serious illness. The average duration of the anagen phase of the hair cycle is 2-6 years, whereas that of the catagen cycle is 2-3 weeks.

Answer 78

Correct choice: A. Montgomery'Â€Â™s tubercles Montgomery'Â€Â™s tubercles are sebaceous glands not associated with hair follicles present on the areola. Tyson'Â€Â™s glands on the labia minora and glans, meibomina and Zeis glands are present on the eyelids , and Fordyce'Â€Â™s spots are located on the buccal mucosa.

Answer 79

Correct choice: B. 8 weeks Epidermal stratification begins at about 8 weeks estimated gestational age and is completed by the 2nd trimester. Epideral stratification occurs when an 'intermediate layer' develops between the epidermal basal cells and the overlying layer of periderm cells. The periderm is an embryonic structure that covers the primitive epidermis until keratinization begins, at which point the periderm sloughs off and contributes to the protective covering of the newborn, the vernix caseosa. This intermediate layer is highly proliferative, such that by 24-25 weeks estimated gestaional age, the epidermis consists of 4 or 5 layers, in addition to the degenerating eriderm.

Answer 80

Correct choice: D. K13 Keratins are divided into acidic (type I) and basic (type II) subtypes. Keratin 13 is a type I keratin which is expressed suprabasally in adult epithelia and is associated with terminal differentiation. Renal transplant recipients have an increased risk of developing skin cancers and multiple warts. Factors contributing to this increased risk include human papillomavirus infection, immunosuppressive therapy, and exposure to ultraviolet radiation. Increased expression of K13 has been demonstrated in high-risk papillomas in this patient population.

Answer 81

Correct choice: A. Granular fluorescence throughout the cytoplasm and nucleus of basal keratinocytes. Granular fluorescence throughout the cytoplasm and nucleus of basal keratinocytes reflect the binding of Ro and La antigens and is unique to SCLE. Cytoid bodies and Immune deposits along dermal-epidermal junction are seen in both DLE and SCLE. Granular deposits along the basement membrane are seen in dermatitis herpetiformis and a chicken-wire pattern of staining is seen in pemphigus vulgaris.

Answer 82

Correct choice: C. 85% Most hair follicles are in anagen, and thus most hair follicles involve growing hair. The longer a hair follicle is anagen, the longer the hair can grow in length. Hairs of the scalp grow approximately 0.4 mm per day, and thus the date of your next hair cut can be accurately calculated.

Answer 83

Correct choice: A. 1 and 3 Retinoids upregulate the transcription of collagens one and thereby strengthening the dermis.

Answer 84

Correct choice: D. A higher degree of dispersion of melanosomes in keratinocytes More darkly pigmented races show a greater production of melanosomes in the melanocyte, melanosomes with a higher degree of melanization, larger melanosomes, a higher degree of dispersion of melanosomes in the keratinocytes, and a slower rate of melanosome degradation.

Answer 85

Correct choice: A. Cytoplasm Both androgen and corticosteroid receptors localize to the cytoplasm. Estrogen receptors are found in the nucleus. Progesterone receptors are distributed in both the nucleus and the cytoplasm.

Answer 86

Correct choice: A. Flegel's Flegel's disease has decreased or absent lamellar granules. AKA hyperkeratosis lenticularis perstans, this is a rare, possibly AD disorder with multiple disc-like keratotic papules predominenty on the distal extremities and feet of older individuals (Bolognia, p 1714).

Answer 87

Correct choice: A. Fibrillins and fibulins Elastic fibers are comprised of elastin as well as microfibrillar proteins including fibrillins and fibulins. Hyaluronic acid is a glycosaminoglycan found in the extracellular matrix of the dermis. Collagen II is the predominant collagen found in cartilage. Laminin 5 and BPAG2 are important anchoring filaments in the basement membrane zone. Desmoplakin and plakoglobulin are proteins found in the anchoring plaques of desmosomes in the epidermis.

Answer 88

Correct choice: A. Desmosine Desmosine and isodesmosine are typical amino acids found in elastic fibers. Glycine, proline and hydroxyproline are found as components of collagen. Isoleucine is not specific for elastin fibers.

Answer 89

Correct choice: E. 24 weeks At 24 weeks, all the layers of the mature epidermis can be identified, and the epidermis is keratinized.

Answer 90

Correct choice: E. Lamina densa Anchoring filaments (smaller than anchoring fibrils) stretch from the plasma membrane through the subbasal dense plaque and the lamina lucida to the lamina densa.

Answer 91

Correct choice: A. Loricrin Loricrin is the major protein component of the cornified cell envelope (CE). Involucrin is cross- linked by transglutaminase in the granular layer to form an insoluble cell boundary. Envoplakin may link the CE to desmosomes and to keratin filaments. Filaggrin is thought to promote aggregation and disulfide bonding of keratin filaments in CE. It is degraded into urocanic acid and pyrrolidone carboxylic acid. Both of which hydrate the stratum corneum and block UV radiation. Laminin V is found in the basement membrane and is not involved in the formation of the cornified cell envelope.

Answer 92

Correct choice: A. on hands/feet Glomus cells are derived from Susquet-Hoyer canals which function to shunt blood from the arterioles to venules and are primarily found on hands and feet. There are two types of glomus tumors, solitary and multiple. The solitary types tend to have paroxysmal pain which can be extreme. Multiple glomus tumors can be a autosomally dominant trait with incomplete penetrance and are less likely to be painful. Both have a predominance on the distal extremities, especially sub- ungual. Two tests are helpful in diagnosing glomus tumors: Hildreth sign - disappearance of pain following application of a tourniquet proximally. Love test - eliciting pain by applying pressure to a precise area with the tip of a pencil.

Answer 93

Correct choice: A. E-cadherin E-cadherin is responsible for the adhesion of Langerhan cells to the epidermis. There are two major subclasses of cadherins which mediate cell adhesion and play a fundamental role in normal development, classic (E-,P-,N-cadherin) and desmosomal (desmoglein and desmocollin). They depend on calcium for their function.

Answer 94

Correct choice: B. Laminin 5 Involvement of Laminin 5 would raise the suspicion for malignancy when found. ~30- 40% of cases may have associated malignancy. Patients with antiepiligrin (laminin 5)CP indicated an increased risk of malignancy that approximates that for adults with dermatomyositis. The risk is particularly high in the first year of disease (E-medicine, www.emedicine.com/derm/topic79.htm). Reports of both lung and gastric carcinomas are seen in the literature with some feeling that gastric malignancy is most common.

Answer 95

Correct choice: D. Ceramide The major component of lamellar granules of the keratinocytes is ceramide. These play a major role in the barrier function of the skin.

Answer 96

Correct choice: A. Lipofuschin Chromhidrosis refers to the secretion of pigmented sweat, most commonly yellow, green or black. It reflects the rich lipofuschin content of apocrine sweat. Extrinsic apocrine chromhidrosis results from staining of sweat and garments by chromogenic bacteria, such as Corynebacterium spp.

Answer 97

Correct choice: D. It is the widest diameter of the hair bulb The critical line of Auber is at the widest diameter fo the hair bulb. Below this line, the bulk of mitotic activity that gives rise to the hair and the inner root sheath occurs. The erector pili muscle inserts in the isthmus region of the follicle. Keratinization first occurs above this line.

Answer 98

Correct choice: B. Spreading bulla phenomenon with pressure on an intact bulla Spreading bulla phenomenon with pressure on an intact bulla is referred to as Asboe-Hansen sign, commonly seen with pemphigus vulgaris. Nikolsky sign can be seen when an intact epidermis shears away from the underlying dermis, leaving a moist surface (seen in pemphigus vulgaris, staphylococcus scalded skin syndrome (SSSS), and toxic epidermal necrosis). Swollen, itchy and or red after stroking the skin is referred to DarierÃ¢Â€Â™s sign and can be seen in systemic mastocytosis or urticaria pigmentosa. Central depression within a lesion when squeezed is referred to as the dimpling sign and is seen in dermatofibromas. Disappearance of color or blanching when the lesion is pressed is commonly found on vascular lesions

Answer 99

Correct choice: B. Stimulus induces the abrupt cessation of mitotic activity in the rapidly dividing hair matrix cells It is frequently seen following administration of cancer chemotherapeutic agents. Stimulus induces the abrupt cessation of mitotic activity in the rapidly dividing hair matrix cells. Occurs within days to weeks following exposure to the inciting agent and is entirely reversible. Frequent causes include antimetabolites, alkylating agents, miotic inhibitors, thallium, boron. Frequent causes include doxorubicin, nitrosureas and cyclophosphamide.

Answer 100

Correct choice: A. Holocrine mechanism The sebaceous lobules have basal germinative cells and central sebocytes, which gradually become more distended with lipid vacuoles until they are shed into the lumen (holocrine secretion).

Answer 101

Correct choice: A. Cystathione synthase Homocystinuria is caused by a mutation in cystathione synthase. The main skin findings are a malar flush, livedo reticularis and leg ulcerations. A characteristic eye finding is the downward displacement of the lens. The other options are involved in abnormalities associated with Ehlers- Danlos syndrome. Lysyl hydroxylase is deficient in Kyphoscoliosis type of EDS. Tenascin X is involves in ~3% of Classical type EDScases. Dermatosparaxis type EDS has recessive mutations in the type I collagen N-peptidase gene.

Answer 102

Correct choice: A. Bullous pemphigoid Bullous pemphigoid is one of the many bullous diseases that may be found on the Ã¢Â€Â˜roofÃ¢Â€Â™ of the blister, the others include pemphigoid gestationis, linear IgA bullous dermatosis, cicatricial pemphigoid. The other answer (except for bullous tinea, in which a salt split would not be performed) are those found on the Ã¢Â€Â˜floorÃ¢Â€Â™ of the blister (lamina densa).

Answer 103

Correct choice: E. Laminin 5 Laminin-5 is a basement membrane extracellular matrix protein that mediates attachment substrate for both adhesion and migration in a wide variety of cell types, including epithelial cells, fibroblasts, neurons and leukocytes and is a preferred adhesion substrate for epithelial cells (Koshikawa et al., 2001). The remaining listed items are part of the desmosomal plaque in the epidermis.

Answer 104

Correct choice: B. 3rd month of gestation Melanocytes begin to synthesize melanin in the 3rd month of gestation.

Answer 105

Correct choice: E. Dapsone Dapsone may be used to treat patients with drug induced linear IgA bullous dermatosis which persist after the offending medication has been discontinued. The other medications listed are rare causes of drug induced linear IgA bullous dermatosis and so should not be used for treatment.

Answer 106

Correct choice: B. Collagen III Granulation tissue begins to form four days after injury and is composed of new capillaries, macrophages, fibroblasts, blood vessels and primarily collagen type III. Formulation of granulation tissue is dependent on the presence of fibronectin and progresses through an orderly sequence of matrix deposition: fibronectin to collagen III then finally collagen I.

Answer 107

Correct choice: E. Junctional epidermolysis bullosa with pyloric atresia JEB with pyloric atresia and ocular cicatricial pemphigoid both have mutations in Beta4integrin. Herlitz type JEB is due to laminin 5. Recessive and dominant dystrophic EB is due to COL17A1 (type VII collagen). JEB with myotonic dystrophy is due to plectin.

Answer 108

Correct choice: C. Follicles develop in a cephalad to caudal direction The first primordial hair follicles form at 9 weeks gestation on the eyebrows, upper lip, and chin. The remaining follicles develop at 4-5 months in a cephalad to caudal direction. New follicles cannot develop in adult skin.

Answer 109

Correct choice: A. Protein A northern blot identifies RNA and a southern blot identifies DNA.

Answer 110

Correct choice: A. Desmocollin 1 Sneddon- Wilkinson disease, also known as sub-corneal pustular dermatosis is due to a defect in desmocollin 1. Desmoglein 1 defect is seen in pemphigus foliaceous and staph scalded skin syndrome. Desmoglein 3 defect is seen in pemphigus vulgaris and intraepidermal neutrophilic IgA dermatosis. BPAg1 is seen in paraneoplastic pemphigus and bullous pemphigoid. BPAg2 is seen in bullous pemphigoid, cicatricial mucous membrane pemphigoid and linear IgA disease.

Answer 111

Correct choice: B. Demonstrate decapitation secretion Apocrine glands show decapitation secretion. Like eccrine glands, apocrine glands are composed of three segments, the intraepidermal duct, the intradermal duct, and the secretory portion. The duct of the apocrine gland usually leads to a pilosebaceous follicle above the entrance of the sebaceous duct. Apocrine glands are found in the axillae, anogenital region, external ear canal (ceruminous glands), in the eyelids (Moll’s glands), and in the breast (mammary glands). Apocrine glans are functional only at puberty. Their initial secretion is odorless.

Answer 112

Correct choice: D. Loricrin The cornified cell envelope is a durable, protein-lipid polymer that eventually acts as a mechanical and chemical barrier on the exterior of cornified cells. In the upper spinous layer, keratohyaline granules release profilagrin and loricrin. Profilaggrin is cleaved to filaggrin and subsequently aggregates keratin filaments. Loricrin is the major protein component of the cornified cell envelope and is bound to the cell membrane by transglutaminases (in addition to other structural proteins like involucrin, keratins, elafin, cystatin A and desmosomal peptides). This forms the highly insoluble proteinaceous component of the cornified cell envelope.

Answer 113

Correct choice: A. 17 Acid keratins are expressed on chromosome 17 and basic keratins on chromosome 12. The other listed options do not have active keratin functions.

Answer 114

Correct choice: D. Integrin Junctional epidermolysis bullosa with pyloric atresia involves a defect in the b4 subunit of the a6b4 integrin. The expression of this protein is limited to the basal layer of the epidermis. This integrin is a transmembrane protein that coordinates a link between the intermediate filaments (keratins) and the extracellular matrix of the basement membrane. The b4 domain mediates an interaction with both plectin and BP180; its absence prevents hemidesmosomal assembly.

Answer 115

Correct choice: B. Macrophage The macrophage is required for wound healing. The macrophages debride tissue, secrete collagenase and stimulate expression of FGF, IL-1, TGF-beta, PDGF and TGF-alpha thus facilitating transition from inflammation to repair.

Answer 116

Correct choice: E. These proteins coordinate linkage between intermediate filaments and extracellular matrix of the basement membrane Defects in the BETA-4 (not alpha-6) domain of integrin result in junctional epidermolysis bullosa with pyloric atresia. Its expression is seen in the basal cell layer and binds to laminins.

Answer 117

Correct choice: A. Pemphigus foliaceus The antigen implicated in pemphigus foliaceus is Desmoglein 1. Desmoglein 1 is targeted in bullous impetigo, but this is an infectious condition, not an autoimmune disease. The antigen in dermatitis herpetiformis is transglutaminase 3. The antigens for both bullous pemphigoid and pemphigoid gestationis are BPAG1 and BPAG2.

Answer 118

Correct choice: B. K6b/17 Keratins 6b & 17 are expressed in the nail bed. K6a/16 is expressed in the outer root sheath and in hyperproliferative keratinocytes, 1/9 in palmoplantar suprabasalar keratinocytes, 2e/10 in the upper spinous and granular cell layers, and 4/13 are expressed in mucosal epithelium.

Answer 119

Correct choice: A. Lamellar granules are uniformly absent In Harlequin ichthyosis, the lamellar granules are uniformly abnormal or absent. On electron microscopy, there is no evidence of the lipid lamellae which form due to lamellar granule discharge into the region between the granular and cornified cells (Fitz v6, p493). This is suggestive of a primary defect in lipid synthesis and protein dephosphorylation resulting in faulty lamellar body formation and secretion (Bolognia, ch. 57). Harlequin fetus/ichthyosis can be divided into three types based on the microscopic appearance of the keratohyaline granules. Type I - normal, Type II - too small to be seen by light microscopy, Type III - absent keratohyaline granules. Demoyokin, band-6 protein (a plaque component) and plakoglobin are desmosomal proteins and not involved in Harlequin ichthyosis. Recently, the gene defect was localized a defect in the ABCA12 protein.

Answer 120

Correct choice: A. When an intact epidermis shears away from the underlying dermis, leaving a moist surface Nikolsky sign can be seen when an intact epidermis shears away from the underlying dermis, leaving a moist surface (seen in pemphigus vulgaris, staphylococcus scalded skin syndrome (SSSS), and toxic epidermal necrosis). Spreading bulla phenomenon with pressure on an intact bulla is referred to as Asboe-Hansen sign, commonly seen with pemphigus vulgaris. Swollen, itchy and or red after stroking the skin is referred to DarierÃ¢Â€Â™s sign and can be seen in systemic mastocytosis or urticaria pigmentosa. Central depression within a lesion when squeezed is referred to as the dimpling sign and is seen in dermatofibromas. Disappearance of color or blanching when the lesion is pressed is commonly found on vascular lesions

Answer 121

Correct choice: A. Are diagnosed at a later stage Acral melanoma is problematic because it is diagnosed at a later stage. It accounts for 5-10% of all melanomas.

Answer 122

Correct choice: B. Keratins 5 and 14 Keratins 5 and 14 are intermediate filaments found in the basal layer of the epidermis that play a role in attaching basal layer keratinocytes to the basement membrane zone. Keratins 1 and 10 are found in more superficial layers of the epidermis. Desmogleins, desmoplakin, and desmoglobin are all components of desmosomes which attach keratinocytes to other surrounding keratinocytes. BPAG1 and BPAG2 are basement membrane proteins.

Answer 123

Correct choice: D. Stratum granulosum The proteins that make up the cornified cell envelope are synthesized in the spinousand granular cell layer. The stratum basale is not involved in production of these proteins and there is no protein synthesis in the stratum corneum. Melanocytes and Langerhans cells are components of the epidermis but are not involved in this process.

Answer 124

Correct choice: E. K5,14 K5 and K14 are expressed in the stratum germinativum (basal layer) and are defective in epidermolysis bullosa simplex. They are still present in the stratum spinosum but are not made de novo in this layer. K4 and 13 are found in mucosal epithelium. K1 and 10 are expressed in suprabasal keratinocytes, K2e and 10 in the upper spinous and granular layers, and K3 and K12 in the cornea.

Answer 125

Correct choice: A. Birt-Hogg-Dube syndrome Fibrofolliculomas are associated with Birt-Hogg-Dube Syndrome and not in the other answer choices.

Answer 126

Correct choice: C. Pseudoxanthoma elasticum There are many genodermatoses that involve elastin. Pseudoxanthoma elasticum shows increased glycosaminoglycans on elastic fibers, calcium deposition and accumulation of fragmented and calcified elastic fibers. Cutis laxa shows decreased desmosine and lysyl oxidase. In Marfan sydrome there is decreased fibrillin I and fragmentation of elastic fibers. Buschke-Ollendorf syndroms shows increased desmosine and increased amount of thickend elastic fibers. Other elastin disease are congenital contractural arachnodactyly from a mutation in fibrillin II and anetoderma which shows decreased desmosine and loss/fragmentation of elastic fibers. Classic type Ehlers- Danlos syndrome is caused by a defect in collagen V and not in elastin. Progeria is caused by a defect in lamin A. EHK is caused by a defect

Answer 127

Correct choice: C. Vater-pacini corpuscle Vater-Pacini corpuscles sense deep touch and vibration. Merkel cells are slow adapting type I mechanoreceptors found among basal keratinocytes. Meissner corpuscles are found in the dermal papilla, especially in the palms and soles. Krase end-bulbs are mucocutaneous end-organs found on the glans penis, prepuce, clitoris, labia minora, and vermillion border of the lip.

Answer 128

Correct choice: A. Darier-roussy disease Darier Roussy disease refers to subcutaneous sarcoid. Lofgrenâ€™s syndrome is sarcoid presenting as erythema nodosum, hilar lymphadenopathy, fever, migrating polyarthritis, and acute iritis. Heerfordtâ€™s is parotid gland enlargement, uveitis, fever and cranial nerve palsies. Kveim- Siltzbach antigen is used rarely in the US but can aid in the diagnosis of sarcoid.

Answer 129

Correct choice: D. Keratins 6 and 16 Keratins 6 and 16 are upregulated in hyperproliferative keratinocytes, outer root sheath, and oral epithelium. A defect in these keratins may result in pachyonychia congenita.

Answer 130

Correct choice: E. Plakoglobin Plakoglobin is an example of an armadillo protein, which links the cytoskeleton associated linking proteins (such as plakins in the case of intermediate filaments and alpha-catenin in the case of actin) to the transmembrane adhesion molecules, termed cadherins. E-cadherin and desmocollin are examples of cadherins. Periplakin and envoplakin are examples of plakin linking proteins.

Answer 131

Correct choice: C. Cytokeratin 20 Cytokeratin 20 is a specific marker for the Merkel cell. Merkel cells are mechanoreceptors located at body sites requiring high tactile sensitivity. Keratinocyte deformation results in a secretion of chemokines by Merkel cells, which make synaptic connection with neurons.

Answer 132

Correct choice: D. Langerhans cell The Langerhans cell is a bone narrow-derived, antigen-presenting cell found in all layers of the epidermis, oral mucosa, esophagus, and vagina. Langerhans cells ingest and process antigens, mature, migrate to a local lymph node, and then present the antigen to a naï¿½ve (or resting) T cell, activating that T cell. The Langerhans cell is central to the pathogenesis of atopic dermatitis, psoriasis, allergic contact dermatitis, and certain infections, such as Leishmaniasis.

Answer 133

Correct choice:E. Pericardium Melanocytes are found in the stria vascularis of the ear, iris, leptomeninges and retina. There are no normal populations of melanocytes found in the pericardium.

Answer 134

Correct choice: C. Swollen, itchy and or red after stroking the skin Swollen, itchy and or red after stroking the skin is referred to Darier's sign and can be seen in systemic mastocytosis or urticaria pigmentosa. Nikolsky sign can be seen when an intact epidermis shears away from the underlying dermis, leaving a moist surface (seen in pemphigus vulgaris, staphylococcus scalded skin syndrome (SSSS), and toxic epidermal necrosis). Spreading bulla phenomenon with pressure on an intact bulla is referred to as Asboe-Hansen sign, commonly seen with pemphigus vulgaris. Central depression within a lesion when squeezed is referred to as the dimpling sign and is seen in dermatofibromas. Disappearance of color or blanching when the lesion is pressed is commonly found on vascular lesions

Answer 135

Correct choice: A. vernix caseosa During the second trimester of fetal development, the periderm is sloughed frommost of the skin surface revealing the underlaying epidermis. The periderm becomes part of the protective coating, vernix caseosa, together with the shed lanugo, sebum and other amniotic fluid materials. Bolognia p.38

Answer 136

Correct choice: C. Laminins provide signaling molecules that interact with other proteins to transmit morphogenetic information to the cell's interior Laminins do transmit signals to the cell's interior. They span from the plasma membrane of basal keratinocytes to the lamina DENSA, not lucida. Laminin 5 (also known as epiligrin) is part of a structural network in the basement membrane that also includes laminin 6.

Answer 137

Correct choice: A. Copper Melanin is synthesized from tyrosine via the action of the enzyme tyrosinase (tyrosine to DOPA to DOPAquinone to melanin). Tyrosinase is a copper containing enzyme. The other elements are not specifically required for melanin synthesis.

Answer 138

Correct choice: B. 14 days Once a basal cell leaves the basal layer in humans, normal transit time to stratum corneum is at least 14 days. Transit time through the stratum corneum to desquamation requires 14 more days.

Answer 139

Correct choice: C. Not all basal cells have the potential to divide Not all basal cells have the potential to divide. Stem cells give rise to transient amplifying cells which give rise to the epidermal keratinocytes. Intermediate filaments in basal cells insert into desmosomes and hemidesmosomes. Keratins 5/14 are predominantly expressed. Microfilaments assist in upward movement of cells. Integrins regulate adhesion and initiation of differentiation.

Answer 140

Correct choice: A. Anchoring filaments attach the basal cell membrane to the lamin lucida The basement membrane zone is seen on staining with PAS stain. It appears as a homogenous band approximately 1 micron thick at the dermo-epidermal junction. The hemidesmosomal complex and basement membrane zone play an integral role in maintaining cellular adhesion. Anchoring filaments (primarily composed of laminin5 and BPAG2) attach the basal cell membrane to the lamina densa NOT lamina lucida.

Answer 141

Correct choice: C. The "spines" seen on pathology are due to desmosomal connections between keratinocytes . The "spines" seen on pathology are due to desmosomal connections between keratinocytes, NOT hemidesmosomes. The hemidesmosomes are present in the cells at the base of the basal layer and are part of the connection between the epidermis and basement membrane. Keratin expression continues in the spinous layer. Keratins 1/10 are synthesized, not keratins 5/14. Keratin 5/14, however, is still present. Keratohyaline granules are typically seen in the granular layer.

Answer 142

Correct choice: C. In white skin the melanosomes form groups within the secondary lysosomes Melanocytes of dark skin synthesize melanosomes larger than those produced in light skin. The number of melanocytes in the epidermis is the same, regardless of the person's race or color: it is the number and size of the melanosomes or pigment granules, continuously synthesized by these melanocytes, that determine differences in skin color. The size of the melanosome is the principle factor in determining how the melanosomes will be distributed within the keratinocytes. The larger the melanosomes of dark skin are individually dispersed within the cytoplasm of keratinocytes: smaller melanosomes of light skin are packaged in membrane-Bound complexes within keratinocytes. Eumelanin is in dark oval melanosomes found in black hair

Answer 143

Correct choice: C. calcium increases, phospholipids decrease, sphingolipids increase Calcium increases, phospholipids decrease, sphingolipids increase. Calcium is needed for desmosome formation and enzyme activation. Phospholipid content of epidermis decreases with differentiation but neutral lipids and sphingolipids (ceramide) increase with differentiation.

Answer 144

Correct choice: E. K1/K9 - palms and soles Keratin 1 and 10 are found in the stratum spinosum. K5 and K14 are found in the basal layer. K3 and K12 are found in the suprabasilar cells of the cornea. K4 and K13 are found in the non- cornifying cells of stratified mucosa. K1 and K9 are found in the palms and soles.

Answer 145

Correct choice: C. Laminin 5 Laminin 5 is found both in the hemidesomsome-anchoring filament complexes and lamina densa. Plectin is found in the hemidesomsome- anchoring filament complexes. Heparin sulfate proteoglycan is found only in the lamina densa, collagen VII in the sublamina densa, and nidogen in the lamina densa.

Answer 146

Correct choice: A. Microtubules Intermediate filaments are composed of keratins, vimentin, desmin, peripherin, neurofilaments, nuclear laminins, and nestin. These are part of cytoskeletal elements.

Answer 147

Correct choice: A. MC1-R MC1-R is the receptor that binds alpha-MSH, and ACTH>alpha-MSH. Defects in this receptor will produce a phenotype including red hair. Agouti is not involved in this process. Agouti describes the banding of hairs seen in some mammals such as dogs, foxes, and mice, which is due to alternating production of eumelanin and pheomelanin occurs. This has not been described in humans (Bolognia, p942). Thehairless gene is associated with alopecia totalis. C-kit mutations are associated with piebaldism and urticaria pigmentosa. Tyrosinase defects are associated with Type I Oculocutaneous albinism.

Answer 148

Correct choice: A. Telogen effluvium All of the listed stressors can induce telogen effluvium. Other causes include traction and some drug exposures. Usually will only involve up to 50% of scalp hairs and will resolve within 2-3 months.

Answer 149

Correct choice: A. Sebaceous glands Sebum is secreted continuously on the skin under hormonal glands. It contains squalene, cholesterol, cholesterol esters, wax, and triglycerides.

Answer 150

Correct choice: B. Plectin EBS with muscular dystrophy is due to a plectin mutation. There are many types of EBS. Anchoring filaments exist within the lamina lucida. They are primarily comprised of laminin 5 and BP180. Laminin 5 is a cross-shaped assembly of 3 classes of polypeptides, a, b, g. The anchoring filaments function as a structural network to which other proteins attach, and they function as signaling molecules that transmit morphogenetic information to transmembrane proteins of the basal cell layer (such as the integrins). Laminin 5 is also called epiligrin and binds to the a6b4 integrin at the hemidesmosome.

Answer 151

Correct choice: A. Holocrine Sebaceous glands exhibit holocrine secretion, whereby the sebocytes disintegrate in transit to the gland center, releasing their sebum contents. Merocrine secretion refers to the formation of intracellular secretory vesicles that translocate to the apical cell surface for secretion. Apocrine secretion refers to the process whereby secretory contents are packaged using the apical cell membrane, and 'pinched off' to achieve secretion.

Answer 152

Correct choice: C. Amnion Type VII collagen is present in anchoring fibrils and amnion. Fetal skin and blood vessels contain type III collagen. The aorta contains type VI collagen. Bone contains type I collagen.

Answer 153

Correct choice: A. Desmosomes Keratin filaments insert into desmosomes and hemidesmosomes in the basal cell layer and into desmosomes in the layers above. Connexins do not bind keratin filaments. Odland bodies and lamellar granules are synonyms. These are a "membrane bounded organelle, specialized for the storage and secretion various substances (surfactant phospholipids, glycoproteins and acid phosphates) which are arranged in the form of tightly packed, concentric, membrane sheets or lamellae. Has some similar properties to, but is distinct from, a lysosome." Desmosomes are multi- protein complexes that function as cell–cell adhesion structures (junctions) in epidermal cells. They also provide attachment sites for the keratin intermediate filament cytoskeleton of keratinocytes. Consequently, these junctions are critical components of a supracellular filament network that traverses the interfollicular epidermis and the epithelia of skin appendages, such as hair follicles.

Answer 154

Correct choice: D. Medulla _ cortex _ hair shaft cuticle _ inner root sheath cuticle _ Huxley's layer _ Henle's layer (As described in correct choice)

Answer 155

Correct choice: B. Langerhans cells Most of the contact allergens are low-molecular weight chemicals, which after penetrating into the skin, have to couple with host proteins to be able to act as full antigens. These are called haptens. Upon epicutaneous application to a naive host, Langerhans cells take up the hapten, Process it and migrate towards the regional lymph nodes, where the anitgen is presented to the naive T cells.

Answer 156

Correct choice: B. Keratin 20 Keratin 20 is reliable immunohistochemical markers for Merkel cells as it is restricted to these cells in the skin. Keratin 7 can be used as a marker for Paget's Disease. S- 100 is frequently used to stain neural cells and melanocytes. Factor XIIIa can be used to differentiate a dermatofibroma from dermatofibroma sarcoma pertuberans (positive in DF; negative in DFSP). LYVE-1 is a marker for lymphatics.

Answer 157

Correct choice: A. Macrophage The macrophage is required for wound healing. Without macrophages, there is no healing. Macrophages debride tissue through phagocytosis and digestion of organisms, tissue debris and effete PMN's. They secrete collagenase and secrete growth factors that facilitate transition from inflammation to repair.

Answer 158

Correct choice: E. Are secretory granules with features of lysosomes Odland bodies (AKA lamellar granules) are lamellated bodies containing ceramide, are found intercellularly in upper level keratinocytes; they discharge contents into the extracellular space at the junction of the granular and horny layers, establish a barrier to water loss, and with filaggrin mediate stratum corneum adhesion. Recent studies suggest that they are a type of secretory granule with features of lysosomes. (They contain lamellar-body-derived enzymes that are important in desquamation.)

Answer 159

Correct choice: C. Sonic hedgehog Sonic hedgehog (Shh), a signaling molecule secreted by ectodermal cells of the developing hair follicle, appears to be critical in mediating the transition from telogen to anagen during postnatal hair cycling

Answer 160

Correct choice: B. It is a member of the plakin family BPAg1 is a member of the plakin family, which includes envoplakin, periplakin, desmoplakin, plectin, and BPAg1. BPAg2 is pathogenic in cicatricial pemphigoid and pemphigoid gestationis. BPAg1 is pathogenic in paraneoplastic pemphigus. Desmoglein 3 is pathogenic in pemphigus vulgaris and coprecipitates with plakoglobin.

Answer 161

Correct choice: B. 9 weeks The first primordial hair follicles form at 9 weeks gestation on the eyebrows, upper lip and chin. The remaining follicles develop at 4-5 months in a cephalad to caudal direction. New follicles cannot develop in adult skin.

Answer 162

Correct choice: E. Secretions are initially odorless Apocrine glands are tubular glands that demonstrate decapitation secretion. Like eccrine glands, the ducts are composed of three segments: intraepidermal duct, intradermal duct and secrectory portion. The duct usually leads to a pilosebaceous follicle above the entrance of the sebaceous duct. They are found in the axillae, anogenital region, external ear canal (ceruminous glands), in the eyelids (MollÃ¯Â¿Â½s glands) and in the breast (mammary glands). These glands are functional starting at puberty. The initial secretions are odorless with the odor being derived from C6 Ã¯Â¿Â½ C11 acids. The most abundant being 3-methyl-2-hexenoic acid.

Answer 163

Correct choice: A. Plectin EBS with muscular dystrophy is due to a mutation in plectin, plectin is also found in skeletal muscle. Keratin 5 and 14 are defective in EBS, EBS herpetiformis, EBS weber cockayne, EBS koebner. Laminin 5 is defective in Herlitz Junctional EB. Collagen VII is mutated in dominant dystrophic EB, Barts syndrome and EB acquisita. Integrin alpha 6/beta 4 is mutated in junctional epidermolysis bullosa with pyloric atresia. Epidermolysis bullosa (EB) is a group of inherited diseases that are characterised by blistering lesions on the skin and mucous membranes. These may occur anywhere on the body but most commonly appear at sites of friction and minor trauma such as the feet and hands. In some subtypes, blisters may also occur on internal organs, such as the oesophagus, stomach and respiratory tract, without any apparent friction. EB should be distinguished from common friction blisters, and from epidermolysis bullosa acquisita (EBA), which is a blistering autoimmune disease that is not inherited and often doesn't develop until adult life. The EB conditions result from genetic defects of molecules in the skin concerned with adhesion. Loss of adhesion results in blister formation. There are four major types of EB based on different sites of blister formation within the skin structure: EB type The site of blister formation within skin (EBS) Epidermolysis bullosa si Epidermis or uppermost layer of skin cells (keratinocytes) (JEB)Junctional epidermolysis Lamina lucida within the basement membrane zone (DEB)Dystrophic epidermolysi Lamina densa and upper dermis Kindler syndrome Mixed pattern or multiple levels within and beneath the basement m Within each of these types of EB, there are various subtypes. Varying degrees of severity that range from mild to severe are found with each EB type. International consensus on the diagnosis and classification of EB has resulted in updated recommendations (2014), based on newer clinical and molecular data.

Answer 164

Correct choice: A. EMA Sebaceous carcinomas stain positive for EMA. The other answer choices are incorrect as they do not stain positive in sebaceous carcinoma.

Answer 165

Correct choice: E. Proline and hydroxyproline Collagen fibers provide tensile strength to the skin and allow it to serve as a protective organ against the external environment. Collagen makes up 80% of the dry weight of the dermis. The structure of collagen is comprised of three alpha chains arranged into a triple helix. The repeating amino acid triplets of the triple helix of collagen are most often Glycine-Proline- Hydroxyproline.

Answer 166

Correct choice: B. 4 Elastin fibers make up 4% of dry weight of the skin, forming a complex meshwork extending from lamina densa of the dermoepidermal junction through the dermis and into the hypodermis. Elastins help return the skin to the normal configuration after being stretched. Elastic fibers are 90% elastin wrapped by fibrillin microfibrils. Fibrillin is mutated in Marfan syndrome. The typical amino acids found in elastic fibers are desmosine and isodesmosine. Elastic fibers turn over slowly in the skin and are damaged by ultraviolet radiation.

Answer 167

Correct choice: B. Substance p Substance P is a neuromediator that binds the tachykinin receptor. It is released upon stimulation of sensory nerve fibers. It has numerous cutaneous functions, including development of skin edema, erythema, and pruritus, upregulation of adhesion molecule expression, release of proinflammatory mediators, etc. Capsaicin causes release of substance P. This has been utilized pharmacologically in conditions such as zoster, in which consistent application of capsaicin leads to depletion of substance P, which in turn can help to reduce/eliminate post-herpetic neuralgia. The other answer choices are also neuromediators that are involved in cutaneous inflammation, but their release is not induced by capsaicin.

Answer 168

Correct choice: D. CD34 CD34+ cells in the bone marrow are the precursors of mast cells. CD3 and CD20 are T and B cell markers respectively. CD6 is found on mononuclear phagocytic cells in the dermis, CD68 is a macrophage marker. Mast cells are normal cells in the body, usually found in the skin and other tissues. Mast cells have a role in the early steps of the body’s coordination of healing responses to an injury. Granules within the mast cells contain histamine and other chemicals. * histamine * leukotriene C4 * prostaglandin D2 * carboxypeptidase * heparin * cathespin G-like protease * tryptase * tumour necrosis factor-A * chymase * interleukin-8 * others When a mast cell is activated, these chemicals are released into the surrounding skin. Mast cell chemicals are mediators of inflammation, and cause the blood vessels to leak, resulting in localised itching, swelling, redness and sometimes blistering. This is what happens normally in insect bites and is thought to be a protective mechanism. For example, a mosquito injects saliva when it bites. The saliva triggers mast cellactivation to a varying degree, depending on the individual's hypersensitivity to the saliva. The unpleasant itch soon persuades the person to try to avoid getting bitten again. Rubbing an area of skin affected by mastocytosis may also activate the mast cells. The rubbed skin becomes reddened, swollen and itchy within a few minutes (Darier sign). In young children, the rubbed area may later blister.

Answer 169

Correct choice: C. Present antigen to naïve t cells in the lymph node. A dermal dendrocyte is a mononuclear phagocytic cell that is a type of antigen presenting cell. It is derived from the bone marrow and found both in the papillary and upper reticular dermis. This cell is highly phagocytic and synonymous with the melanophage that has ingested pigment. Dermal dendrocytes are likely very important to the afferent limb of the immune response.

Answer 170

Correct choice: B. Lichen planopilaris Lichen planopilaris is a chronic, scarring condition that results in permanent loss of hair and destruction of the hair follicles. Defect in lipid metabolism and peroxisome biogenesis may contribute to LPP pathogenesis. Medications that act as PPAR agonists, such as pioglitazone, may have a role in controlling the progression of this disease. (Karnik P, et al. (2009) Hair follicle stem cell-specific PPAR deletion causes scarring alopecia. J Invest Dermatol 129(5):1243-57)

Answer 171

Correct choice: E. Results from sudden illness or surgery Telogen effluvium is an excessive loss of club hairs from the normal resting follicles of the scalp. The follicle is pushed from anagen to catagen to telogen. There is no inflammatory process involved. Causes of telogen effluvium are illness, surgery, parturition, fever, drugs, traction, starvation, and hypervitaminosis A. Usually, the hair loss only involves less than 50% of the scalp. There is no specific therapy, and most cases are self-resolving within months.

Answer 172

Correct choice: A. Neutrophil Neutrophils migrate with monocytes concurrently, but arrive first in great numbers because of their abundance in circulation. Chemoattractants for the PMNs are fibrinogen, fibrin split products, C5a and leukotrienes. If wound contamination is controlled, PMN migration ceases within a few days and they become entrapped within the wound clot, undergo apoptosis or are phagocytosed by macrophages.

Answer 173

Correct choice: C. Increased involucrin In psoriasis, involucrin levels are increased. In contrast, filaggrin and loricrin levels are diminished. Decreased lamellar bodies are implicated in Flegel’s disease andHarlequin icthyosis. Tissue transglutaminase I is faulty in lamellar icthyosis and non-bullous congenital icthyosiform erythroderma.

Answer 174

Correct choice: A. C-polymodal nociceptor class nerves Itch is transmitted primarily by C-polymodal nociceptor class nerves. These are small diameter unmyelinated nerves that carry pain, thermal, mechanical and pruritic stimuli. A-delta fibers carry pain, thermal, mechanical and in some cases pruritic stimuli. A-beta fibers carry light touch and motion stimuli. Parasympathetic post-ganglionic fibers do not contribute to cutaneous pruritus

Answer 175

Correct choice: E. Ferrochelatase All of the listed enzymes are copper containing or dependent except ferrochelatase. Lysyl oxidase facilitates crosslinking of fibrillin in elastic fibers. ATP7a is deficient in Menkes Kinky Hair Syndrome. Cystathione beta-Synthase is defective in homocystinuria. Tyrosinase catalyzes the first 2 steps, and at least 1 subsequent step, in the conversion of tyrosine to melanin. Ferrochelatase mutation leads to excess protoporphyrin production and photosensitivity.

Answer 176

Correct choice: D. Plectin is a member of the plakin family Plectin is a hemidesmosomal protein and is not present in the desmosome. It links intermediate filaments to the plasma membrane, crosslinks hemidesmosomal proteins, mutations result in epidermolysis bullosa simplex with muscular dystrophy and is a member of the plakin family.

Answer 177

Correct choice: A. Moll's gland There are several types of specialized sebaceous glands that are not associated with a hair follicle. They include Montgomery's areolar tubercle, Fordyce spots of the lip, Glands of Zeis of the cutaneous eyelid, and Meibomian glands of the eyelid. Moll's gland of the eyelid are a modified apocrine gland.

Answer 178

Correct choice: C. Vascular smooth muscle cells Glomus cells are derived from Suquet-Hoyer canals. They are vascular smooth muscle cells that allow the rapid shunting of blood from the arterioral to venularsystem, bypassing the capillaries. This process occurs primarily on the palms and soles.

Answer 179

Correct choice: D. Are singly dispersed in the basal layer in white skin Several differences exist that may explain the heterogeneity of skin color. The number of melanocytes are the same; however, there are several differences in the melanosomes. Differences in skin color can be attributed to five factors. In racially heavily pigmented skin, (1) there is greater production of melanosomes in melanocytes, (2) individual melanosomes show a higher degree of melanization, (3) melanosomes are larger, (4) the melanosomes are dispersed to a greater degree in the keratinocytes, and (5) there is a slower rate of degradation.

Answer 180

Correct choice: E. Il-23 IL-2 is a cytokine that primarily produced by T lymphocytes and acts on Other T lymphocytes as a growth factor for both survival anddifferentiation. IL-3 is also produced by T lymphocytes and acts as a growth factor for cells of the myeloid lineage. IL-17 is an effector cytokine that is implicated in the pathogenesis of psoriasis and produced by Th17 cells. IL-22 is also an effector cytokine produced by T lymphocytes that contributes to epidermal acanthosis in psoriasis. All of these cytokines are not secreted from epidermal keratinocytes. IL-23, which promotes Th17 effector function, is secreted by epidermal keratinocytes and upregulated in psoriasis. The p40 subunit of IL-23 is the target of drug ustekinimab used to treat psoriasis

Answer 181

Correct choice: B. During the 2nd week of wound healing Wound healing tends to be a predictable process that begins initially with the inflammatory stage. During this stage, clot formation occurs. This is the initial step in wound healing. Platelets, neutrophils and macrophages all migrate to the wound and secrete many mediators of wound healing. Epithelialization then begins hours after injury. This is followed by granulation tissue formation (four days after injury) and angiogenesis (first week of repair). Wound contraction ensues during the second week of healing.

Answer 182

Correct choice: D. Intercellular IgG and C3 and linear IgG and C3 along the basement membrane zone Senear-Usher syndrome, or pemphigus erythematosus, is a variant of pemphigus foliaceus characterized by crusted papules and plaques with a seborrheic distribution (malar region, scalp, upper chest and back). They demonstrate in-vivo IgG and C3 deposition on keratinocyte cell membranes and the basement membrane zone, in addition to circulating anti-nuclear antibodies.

Answer 183

Correct choice: E. Keratinocytes S100 is sensitive for melanocytes and melanoma, but not specific as it also stains langerhans cells, eccrine cells, schwann cell, adipocytes, and chondrocytes. It is negative in keratinocytes and can help discriminate melanoma from pagetoid bowens or spindle cell squamous cell carcinoma.

Answer 184

Correct choice: D. TGF-alpha Platelets release PDGF, TGF-alpha and TGF-beta which promote new tissue growth. FGF and IL-1 are released from monocytes as growth factors (monocytes also release PDGF, TGF-alpha and TGF-beta). ADP is released from platelets, but is not functioning as a growth factor. Neutrophil chemotactic factor is released from mast cells and is an inflammatory mediator.

Answer 185

Correct choice: A. NC16A of BP180 The NC16A domain of BP180 is the target of autoantibodies in bullous pemphigoid. It interacts with alpha-6 integrin extracellularly.

Answer 186

Correct choice: A. Buschke Ollendorf LEMD3 or MAN1 is mutated in Buschke-Ollendorf syndrome. Common skin findings include dermatofibrofibrosis lenticularis disseminata. The radiographic finding commonly seen is osteopoikilosis. The gene defect was recently described as MAN1/LEMD3, a gene encoding for a nuclear membrane protein. Albright Hereditary Osteodystrophy is caused by inactivation of GNAS1, Goltz is an x-linked dominant condition with unknown pathogenesis, McCune-Albright syndrome is caused by an activation of GNAS1. Menke's Syndrome is caused by a defect in ATP7A/MKN on Xq13.

Answer 187

Correct choice: A. Plakin BP230 is a member of the plakin family and is homologous to desmoplakin and is intracellular. It attaches intermediate filaments to hemidesmosomal plaque. The remaining options are not part of the plakin family.

Answer 188

Correct choice: A. Mononuclear phagocytic cells The mononuclear phagocytic cell includes monocytes, macrophages and dermal dendrocytes. All phagocytic skin macrophages express CD11c and CD6. Fibroblasts do not produce a CD marker. Mast cells are derived from bone marrow-residing CD34+ stem cells. They do not produce CD11c or CD6.

Answer 189

Correct choice: C. 0.4 mm/day Hair grows at an average of 0.4 mm/day. The other options are incorrect.

Answer 190

Correct choice: E. K16 K16 and K6 act as markers for hyperproliferative keratinocytes. They are found in skin disease such as psoriasis, warts, actinic keratoses, and SCC's.

Answer 191

Correct choice: A. Type VII collagen Type VII collagen is the target for both dystrophic EB and bullous SLE. It is also the target for EB acquisita.

Answer 192

Correct choice: E. Collagen type VII Dystrophic epidermolysis bullosa results from mutations in Type 7 collagen. Type I collagen mutations are associated with osteogenesis imperfecta. Antibodies to Type II collagen are associated with relapsing polychondritis. Mutations in type V collagen result in the classic form of Ehlers Danlos while mutations in type III collagen result in the vascular form of Ehlers Danlos.

Answer 193

Correct choice: B. Found on the vermillion border of the lips Krause end bulbs are mucocutaneous receptors found on the glans penis, clitoris, labia minora, perianal area, and vermillion border of the lips. Papillary nerve endings are free nerve endings found at the orifice of the hair follicle and particularly sensitive to cold. Meissner's corpuscles are ovoid, elongated mechanoreceptors located in the dermal papillae of digital skin that detect touch and light pressure. Pacinian (Vater- Pacini) corpuscles exist in the deep dermis and within the subcutis in weight-bearing sites and function as adapting mechanoreceptors that respond to vibrational stimuli.

Answer 194

Correct choice: A. 1st trimester Hair follicles begin in the third month of fetal life as a downgrowth of cells from the epidermis (3rd month=12th week=1st trimester).

Answer 195

Correct choice: A. Modified sebaceous glands Meibomian glands of the eyelids are modified sebaceous glands. Sebaceous glands are found everywhere on the skin except the palms and soles. Montgomery's areolar tubercles consist of several sebaceous lobules feeding into a lactiferous duct. Ceruminous glands are apocrine glands of the external ear canal. Apocrine glands in the eyelids are Moll's glands.

Answer 196

Correct choice: B. Glycogen In week 7 of embryogenesis the surface ectoderm produces two layers. The external layer is the periderm which contains glycogen and gives rise to the stratum corneum by week 21. The other layer is the stratum germinativum.

Answer 197

Correct choice: E. 36 keratinocytes One melanocyte and 36 keratinocytes make up one epidermal melanin unit. This melanocytes transfers pigment to these keratinocytes.

Answer 198

Correct choice: D. There are equal numbers of melanocytes Individuals with darker pigmentation have an equal ratio of melanoyctes to keratinocytes. Darker pigmentation is related to an increased number of melanosomes, increased melanization, greater size of melanosomes, and slower degradation.

Answer 199

Correct choice: D. Huxley’s layer contains melanin The inner root sheath is composed of three layers, which are the inner root sheath cuticle, Huxley layer, Henle layer. None of these layers contain melanin. All three layer keratinize by trichohyaline granules and disintegrate when they reach the isthmus of the hair follicle.

Answer 200

Correct choice: D. Collagen V Classical types of Ehrlers-Danlos are manifested by varying degrees of hyperextensible skin, easy bruising, wide, atrophic scars, and hypermobile joints. The genetic defect is in Collagen V. Elastin is mutated in Cutis Laxa. ABCC6 is defective in Pseudoxanthoma elasticum. Cystathionine beta-synthase is mutated in homocystinuria.

Answer 201

Correct choice: A. Collagen I Collagen type I is mutated in osteogenesis imperfecta. The COL1A2 gene is located on 7q22 and the COL1A1 is on 17q22. The other listed collagens are not involved in osteogenesis imperfecta. Collagen II is in cartilage and vitreous, Collagen III is in fetal skin, blood vessels and intestines, Collagen IV is in basement membranes and Collagen VII in anchoring fibrils and amnion.

Answer 202

Correct choice: C. Mast cell Electron microscopy of mast cells demonstrates large long villi at the periphery and round or oval secretory granules. Langerhans cells show a folded nucleus and rarely phagocytized melanosomes on electron microscopy. Their characteristic feature is the presence of Birbeck granules whose disk shape with one or two vesicles at either end represents a tennis raquet. Examination of melanocytes shows an absence of tonofilaments or desmosomes with characteristic melanosomes in various stages of formation. Macrophages often contain phagocytized material within phagosomes.

Answer 203

Correct choice: D. KIT Mucosal melanomas tend to have an activating mutation in KIT. GNAQ mutations are seen in both uveal melanomas and blue nevi. Cyclin dependant kinase 4/6 binds cyclin D and together phosphorylate Retinoblastoma. MDM2 targets p53 for ubiquitination.

Answer 204

Correct choice: D. Type VII Collagen Anchoring fibrils are made of Type VII collagen. Anchoring plaques are made of Type IV collagen, and interact with a network of Type I And Type III collagen fibers in the dermis.

Answer 205

Correct choice: E.Cytokeratin (CK) 20 is a reliable marker for Merkel cells. CD20 is a marker for B-cells and CD3 is a T-cell marker. HMB-45 is used in staining for immature melanosomes and is reactive in melanoma. CD34 is used to stain dermatofibrosarcoma protuberans.

Answer 206

Correct choice: A. Keratinocytes, Melanocytes, Merkel cells, Langerhan cells The adult epidermis is composed of three basic cell types: Keratinocytes, melanocytes, and Langerhans cells. An additional cell, the Merkel cell, can be found in the basal layer of the palms and soles, the oral and genital mucosa, the nail bed, and the follicular infundibula.