Musculoskeletal, Skin, & Connective Tissue Flashcards Preview

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Flashcards in Musculoskeletal, Skin, & Connective Tissue Deck (139):

Epidermis Layers

Surface to Base
-Stratum Corneum (keratin)
-Stratum Lucidum
-Stratum Granulosum
-Stratum Spinosum (spines = desmosomes)
-Stratum Basale (stem cell site)


Sebaceous Gland

-Holocrine secretion of sebum
-Associated with hair follicle


Eccrine Gland

-Secretes Sweat
-Found throughout body


Apocrine Gland

-Secretes milky viscous fluid
-Found in axillae, genitalia, & areolae
-Does not become functional until puberty
-Malodorous b/c of bacterial action


Epithelia Cell Junction: Tight Junction

(zonula occludens)
-prevents paracellular movement of solutes; composed of claudins & occludins


Epithelia Cell Junction: Adherens Junction

(zonula adherens)
-below tight junction, forms "belt" connecting actin cytoskeletons of adjacent cells with CADherins (Ca2+ dependent adhesion proteins)
-loss of E-cadherin promotes metastasis


Epithelia Cell Junction: Desmosome

(macula adherens)
-structural support via keratin interactions
-autoantibodies cause pemphigus vulgaris


Epithelia Cell Junction: Gap Junction

-channel proteins called connexons permit electrical & chemical communications between cells


Epithelia Cell Junction: Hemidesmosome

-connects keratin in basal cells to underlying basement membrane
-autoantibodies: bullous pemphigoid (hemidesmosomes are down "bullow"


Epithelia Cell Junction: Integrins

-membrane proteins that maintain integrity of basement membrane by binding to laminin in BM


Unhappy Triad/Knee Injury

-common injury in contact sports; lateral force applied to a planted leg
-triad includes tear of the ACL, MCL, & meniscus (classically medial, but lateral more common)
-Often requires surgical ACL reconstruction
-"anterior" and "posterior" in ACL & PCL refer to sites of tibial attachement


Positive Anterior Drawer Sign

ACL tear


Abnormal Passiv Abduction of knee?

MCL tear


Where do you put pudendal nerve block to relieve pain of delivery?

Ischial spine


Where is the appendix located?

2/3 of the way from the umbilicus to the anterior superior iliac spine (McBurney's point)


Where do you perform a lumbar puncture?

iliac crest


Rotator Cuff Muscles

-Supraspinatus-abducts arm initially (before deltoid); most common rotator cuff injury
-Infraspinatus-laterally rotates arm; pitching injury
-Teres Minor-adducts and laterally rotates arm
-Subscapularis-medially rotates and adducts arm

-innervated by C5-C6


Wrist Bones

-Scaphoid, Lunate, Triquestrum, Pisiform, Hamate, Capitate, Trapezoid, Trapezium

-Scaphoid is most commonly fractured carpal and is prone to avascular necrosis owing to retrograde blood supply
-Dislocation of lunate may cause acute carpal tunnel syndrome


Carpal Tunnel Syndrome

-entrapment of median nerve in carpal tunnel; nerve compression leads to paresthesia, pain, and numbness in distribution of median nerve


Axillary Nerve

Injury: fractured surgical neck of humerus, dislocation of humeral head

Motor Defect: Deltoid, arm abduction at shoulder

Sensory Deficit: over deltoid muscle

Sign: Atrophied deltoid


Radial Nerve

Injury: Fracture at midshaft of humerus; "Saturday night palsy" (extended compression of axila by back of chair or crutches)

Motor Defect: BEST extensors: Brachioraadialis, Extensors of wrist and fingers, Supinator, Triceps

Sensory Deficit: Posterior arm & dorsal hand & thumb

Sign: Wrist Drop


Median Nerve

Injury: Fracture of supracondylar humerus (proximal lesion)

Motor Defect: Opposition of thumb, Lateral finger flexion, Wrist Flexion

Sensory Deficit: Dorsal & Palmar aspects of lateral 3.5 fingers, thenar eminence

Sign: "Ape Hand" "Pope's Blessing"


Ulnar Nerve

Injury: Fracture of medial epicondyle of humerus, "funny bone" (proximal lesion)

Motor Defect: Medial finger flexion, Wrist Flexion

Sensory Deficit: Medial 1.5 fingers, hypothenar eminence

Sign: Radial deviation of wrist upon wrist flexion


Musculocutaneous Nerve

Injury: Upper trunk compression

Motor Defect: Biceps, brachialis, coracobrachialis, Flexion of arm at elbow

Sensory Deficit: Lateral forearm


Erb-Duchenne palsy

"waiter's tip"
-Traction of tear of the upper trunk of the brachial plexus (C5 & C6 roots); seen in infants following trauma during delivery
-Findings: limb hangs by side (paralysis of abductors), medially rotated (paralysis of lateral rotators), forearm is pronated (loss of biceps)


Klumpke's palsy & thoracic outlet syndrome

-An embryologic or childbirth defect affecting inferior trunk of brachial plexus (C8, T1); a cervical rib can compress subclavian artery & inferior trunk, resulting in throacic outlet syndrome
-atrophy of the thenar & hypothenar eminences
-atrophy of the interosseuous muscles
-sensory deficits on the medial side of the forearm & hand
-disappearance of the radial pulse upon moving the head toward the ipsilateral side


Distortions of the Hand

-"clawing" is easily conceptualized as loss of the lumbricals, which flex the MCP joints and extend both the DIP and PIP joints


Ulnar Claw

-Can be caused by long-standing injury to ulnar nerve at hamate (by falling into outstretched hand)
-Distal ulnar nerve lesion leads to loss of medial lumbrical function which lead to inability to extend 4th & 5th digits "clawing" when trying to open the hand


Median Claw

-Can be caused by carpal tunnel syndrome of dislocated lunate
-Distal median nerve lesion (after branch containing C5-C7 branches off to feed forearm flexors) leads to loss of lateral lumbrical function; 2nd and 3rd digits are clawed upon attempted finger extension


"Pope's Blessing"

-Proximal median nerve lesion causes loss of lateral finger flexion & thumb opposition
-When asked to make fist, 2nd and 3rd digits remain extended & thumb remains unopposed, which looks like the hand of benediction


"Ape Hand"

-Proximal median nerve lesion leads to loss of opponens pollicis muscle function which causes unopposable thumb (inability to abduct thumb)


Klumpke's total claw

-Lesion of lower trunk (C8, T1) of brachial plexus leads to loss of function of all lumbricals; forearm finger flexors (fed by part of median nerve with C5-C7) and finger extensors (fed by redial nerve) are unopposed leading to clawing of all digits


Long Thoracic Nerve

Serratus anterior - anchors scapula to thoracic cage
-used for abduction above horizontal position
-can be injured in mastectomy (winged scapula & ipsilateral lymphedema



-Opponens pollicis, Abductor pollicis brevis, Flexor policis brevis
-oppose, abduct, flex



-Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi
-oppose, abduct, flex


Dorsal Interosseous Muscles

abduct the fingers


Palmar Interosseous Muscles

adduct the fingers


Lumbrical Muscles

flex at the MCP joint, extend PIP & DIP joints


Obturator Nerve

Injury: Anterior hip dislocation

Motor Deficit: Thigh Adduction

Sensory Deficit: Medial Thigh


Femoral Nerve

Injury: Pelvic Fracture

Motor Deficit: Thigh flexion and leg extension

Sensory Deficit: Anterior thigh & medial leg


Common Peroneal Nerve

Injury: Trauma or compression of lateral aspect of leg or fibula neck fracture

Motor Deficit: Foot eversion & dorsiflexion; toe extension; foot drop, foot slap, steppage gait

Sensory Deficit: Anterolateral leg & dorsal aspect of foot

PED = Peroneal Everts & Dorsiflexes (foot drop)


Tibial Nerve

Injury: Knee trauma

Motor Deficit: Foot inversion & plantarflexion; toe flexion

Sensory Deficit: Sole of foot

TIP = Tibial Inverts & Plantarflexes (can't stand on tiptoes if injured)


Superior Gluteal Nerve

Injury: Posterior hip dislocation or polio

Motor Deficit: THigh abduction (+ Trendelenburg sign-contralateral hip drop when standing on leg ipsilateral to site of lesion)


Inferior Gluteal Nerve

Injury: Posterior hip dislocation

Motor Deficit: Can't jump, climb stairs, or rise from seated position; can't push inferiorly (downward)


Sciatic Nerve

-posterior thigh, splits into common peroneal & tibial nerve


Muscle Contraction

1. Action Potential depolarization opens presynaptic voltage-gated Ca2+ channels, inducing neurotransmitter release
2. Postsynaptic ligand binding leads to muscle cell depolarization in motor end plate
3. Depolarization travels along muscle cell & down T-tubule
4. Depolarization of the voltage-sensitive dihydropyridine receptor, mechanically coupled to the ryanodine receptor on the sarcoplasmic reticulum, induces a conformational change causing Ca2+ release from the SR
5. Released Ca2+ binds to troponin C, causing a conformational change that moves tropomyosin out of the myosin-binding groove on actin filaments
6. Myosin releases bound ADP & is displaced on the actin filament (power stroke), contraction results in shortening of H & I bands and b/w Z lines (HIZ shrinkage), but the A band remains the same length


Type 1 Muscle Fibers

-Slow twitch, red fibers resulting from inc. mytochondria & myoglobin concentration (inc. oxidative phosphorylation) leads to sustained contraction

-1 slow red ox


Type 2 Muscle Fibers

-Fast twitch, white fibers resulting from dec. mitochondrial & myoglobin concentration (inc. anaerobic glycolysis); weight training results in hypertrophy of fast-twitch muscle fibers


Bone Formation: Endochondral Ossification

-Bones of axial & appendicular skeleton, and base of the skull
-Cartilaginous model of bone is first made by chondrocytes
-Osteoclasts & osteoblasts later replace with woven bone & then remodel to lamellar bone
-In adults, woven bone occurs after fractures and in Paget's disease


Membranous Ossification

-Bones of calvarium & facial bones
-Woven bone formed directly without cartilage
-Later remodeled to lamellar bone



Build bone by secreting collagen & catalyzing mineralization
-Differentiate from mesenchymal stem cells in periosteum



-Multinucleated cells that dissolve bone by secreting acid and collagenases
-Differentiate from monocytes/macrophages


Parathyroid Hormone

-At low, intermittent levels, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect)
-Chronic high PTH levels (primary hyperparathyroidism) cause catabolic effects (osteitis fibrosa cystica)



-Inhibits apoptosis in bone-forming osteoblasts & induces apoptosis in bone-resorbing osteoclasts
-under estrogen deficiency (surgical or postmenopausal), excess remodeling cycles & bone resorption lead to osteoporosis



-Failure of longitudinal bone growth (endochondral ossification), short limbs
-Membranous ossification is not affected, large head relative to limbs
-Constitutive activation of fibroblast growth factor receptor (FGFR3) actually inhibits chondrocyte proliferation > 85% of mutations occur sporadically are associated with advanced paternal age, but the condition also demonstrates autosomal-dominant inheritance
-common cause of dwarfism
-normal life span and fertility



-Trabecular (spongy) bone loses mass and interconnections despite normal bone mineralization & lab values (serum Ca2+ and PO4-)
-Can lead to vertebral crush fractures: acute back pain, loss of height, kyphosis


Osteoporosis: Type I

-Postmenopausal, inc. bone resorption due to dec. estrogen levels
-Femoral neck fracture, distal radius (Colle's) fractures


Osteoporosis: Type II

-Senile osteoporosis: affects men and women > 70 yrs of age
-Prophylaxis: regular weight-bearing exercise & adequate Ca and Vit D intake throughout adulthood
-Treatment: estrogen (SERMs) and/or calcitonin; bisphosphonates or pulsatile PTH for severe cases. Glucocorticoids are contraindicated



"marble bone disease"
-Failure of normal bone resorption due to defective osteoclasts, thickened, dense bones that are prone to fracture. Bone fills marrow space, causing pancytopenia, extramedullary hematopoiesis.
-Mutations (carbonic anhydrase II) impair ability of osteoclast to generate acidic env. necessary for bone resorption. X-ray show bone-in-bone appearance.
-Can result in cranial nerve impingement and palsies as a result of narrowed foramina
-Bone marrow transplant is potentially curative as osteoclasts are derived from monocytes



rickets - kids, osteomalacia - adults
-Vit. D deficiency, due to defective mineralization/calcification of osteoid, soft bones that bow out
-Dec. vit D, dec. serum Ca, inc. PTH secretion, dec. serum phosphate
-hyperactivity of osteoblasts, inc. alkaline phos. (osteoblasts require alkaline environment)


Paget's Disease of Bone
(osteitis deformans)

-Common, localized disorder of bone remodeling caused by inc. in both osteoblastic & osteoclastic activity
-Serum Ca, phosphorus, PTH levels are normal
-Inc. ALP
-Mosaic "woven" bone pattern, long bone chalk-stick fractures, inc. blood flow from inc. arteriovenous shunts may cause high-output heart failure
-inc. risk of osteogenic sarcoma
-Hat size inc.. hearing loss common due to auditory foramen narrowing


Polyostotic Fibrous Dysplasia

-Bone is replaced by fibroblasts, collagen, and irregular bony trabeculae
-McCune-Albright syndrome is a form of polyostotic fibrous dysplasia characterized by multiple unilateral bone lesions associated with endocrine abnormalities (precocious puberty) and cafe-au-lait spots


Primary Bone Tumors: Giant Cell Tumor (osteoclastoma)

-benign tumors
-20-40 yrs of age
-epiphyseal end of long bones
-locally aggressive benign tumor often around the distal femur, proximal tibial region (knee)
-"Double bubble" or "soap bubble" appearance on x-ray
-Spindle-shaped cells with multinucleated giant cells


Primary Bone Tumors: Osteochondroma (exostosis)

-most common benign tumor
-males <25 yrs of age
-mature bone with cartilaginous cap, commonly originates from long metaphysis
-malignant transformation to chondrosarcoma is rare


Primary Bone Tumors: Osteosarcoma (osteogenic sarcoma)

-2nd most common primary malignant bone tumor (after multiple myeloma)
-Male>female, 10-20 yrs of age (primary)
-Predisposing factors: Paget's disease of bone, bone infarcts, radiation, familial retinoblastoma
-Metaphysis of long bones, often around distal femur, proximal tibial region (knee)
-Codman's triangle (from elevation of periosteum) or sunburst pattern on x-ray
-aggressive. Treat with surgical en bloc resection (with limb salvage) & chemotherapy


Primary Bone Tumors: Ewing's Sarcoma

Malignant Tumors
-Boys < 15 yrs of age
-commonly appears in diaphysis of long bones, pelvis, scapula, & ribs
-Anaplastic small blue cell malignant tumor
-Extremely aggressive with early metastases, but responsive to chemo
-"Onion skin" appearance in bone ("going out for Ewings and onion rings")
-Associated with t(11;22) translocation


Primary Bone Tumors: Chondrosarcoma

Malignant Tumors
-men 30-60 yrs of age, usually located in pelvis, spine, scapula, humerus, tibia, or femur
-malignant cartilaginous tumor
-may be of primary origin or from osteochondroma
-expansile glistening mass within the medullary cavity



-Mechanical-joint wear and tear destroys articular cartilage
-Subchondral cysts, sclerosis, osteophytes (bone spurs), eburnation (polished, ivory-like appearance of bone), Heberden's nodes (DIP), and Bouchard's nodes (PIP), no MCP involvement
-age, obesity, joint deformity
-pain in weight-bearing joints after use (at the end of the day), improving with rest
-Knee cartilage loss begins medially "bowlegged"
-noninflammatory, no systemic symptoms
Treat: NSAIDs, intra-articular glucocorticoids


Rheumatoid Arthritis

-Autoimmune-inflammatory destruction of synovial joints, Type III hypersensitivity
-Pannus formation in joints (MCP, PIP), subcutaneous rheumatoid nodules (fibrinoid necrosis), ulnar deviation of fingers, subluxation, Baker's cyst (in popliteal fossa), no DIP involvement
-Females>males, 80% have +Rh factor (anti-IgG); anti-cyclic citrullinated peptide ab is more specific
-Strong association with HLA-DR4
-Morning stiffness lasting >30 min. & improving with use, symmetric joints involvement, systemic symptoms (fever, fatigue, pleuritis, pericarditis)
-Treatment: NSAIDs, glucocorticoids, disease-modifying agents (methotrexate, sulfasalazine, TNF-alpha, inhibitors)


Sjogren's Syndrome

-Lymphocytic infiltration of exocrine glands, especially lacrimal & salivary
-Classic Triad: Xerophthalmia (dry eyes, conjunctivitis, "sand in eyes"), Xerostomia (dry mouth, dysphagia), Arthritis
-Parotid enlargement, inc. risk of B-cell lymphoma, dental caries. Autoantibodies to ribonucleoprotein antigens: SS-A (Ro), SS-B (La)
-Predominantly affects females b/w 40 & 60 years of age
-associated with rheumatoid arthritis


Findings in Gout

-Precipitation of monosodium urate crystals into joints due to hyperuricemia, which can be caused by Lesch-Nyhan syndrome, PRPP excess, dec. excretion of uric acid (thiazide diuretics), inc. cell turnover, or von Gierke's disease
-90% due to underexcretion; 10% due to overproduction
-Crystals are needle shaped & negatively birefringent = yellow crystals under parallel light
-more common in men


Symptoms in Gout

-Asymmetric joint distribution
-Joint is swollen, red, painful
-Classic: painful MTP joint of the big toe (podagra)
-Tophus formation (often on external ear, olecranon bursa, or Achilles tendon)
-Acute attack tends to occur after a large meal or alcohol consumption (alcohol metabolites compete for same excretion sites in kidneys as uric acid, causing dec. uric acid secretion & subsequent buildup in blood)


Treatment of Gout

Acute: NSAIDs (indomethacin), glucocorticoids
Chronic: Xanthine oxidase inhibitors (allopurinol, febuxostat)



-Caused by deposition of Ca pyrophosphate crystals within the joint space
-Forms basophilic, rhomboid crystals that are weakly positively birefringent
-Usually affects large joints (classically the knee)
- >50 yrs old; both sexes affected equally
-Treatment: NSAIDs for sudden, severe attacks; steroids, & colchicine
-Blue when parallel to the light


Infectious Arthritis

-S. aureus, Streptococcus, & Neisseria gonorrhoeae are common causes
-Gonococcal arthritis is an STD that presents as a migratory arthritis with an asymmetric pattern
-Affected joint is swollen, red, painful
-STD = Synovitis (knee), Tenosynovitis (hand) & Dermatitis (pustules)


Osteonecrosis (avascular necrosis)

-Infarction of bone marrow
-Pain associated with activity, caused by trauma, high-dose corticosteroids, alcoholism, sickle cell
-most common site is femoral head


Seronegative Spondyloarthropathies

-Arthritis without rheumatoid factor (no anti-IgG ab)
-Strong association with HLA-B27 (gene that codes for HLA MHC class I)
-Occurs more often in males


Psoriatic Arthritis

Seronegative Spondyloarthropathies
-Joint pain & stiffness associated with psoriasis
-Asymmetric & patchy involvement
-Dactylitis "sausage fingers", "pencil-in-cup" deformity on x-ray
-seen in fewer than 1/3 of patients with psoriasis


Ankylosing Spondylitis

Seronegative Spondyloarthropathies
-Chronic inflammatory disease of spine & sacroiliac joints, ankylosis (stiff spine due to fusion of joints), uveitis, & aortic regurgitation


Inflammatory Bowel Disease

Seronegative Spondyloarthropathies
-Crohn's disease & ulcerative colitis are often accompanied by anklyosing spondylitis or peripheral arthritis


Reactive Arthritis (Reiter's Syndrome)

Classic Triad: Conjunctivitis (and anterior uveitis), Urethritis, Arthritis

"Can't see, can't pee, can't climb a tree"
-Post-GI or chlamydia infections


Systemic Lupus Erythematosus

-90% female & b/w 14-45
-most common & severe in black females
-Presentation: fever, fatigue, weight loss, Libman-Sacks endocarditis (verrucous, wart-like, sterile vegetations on both sides of valve), hilar adenopathy, and Raynaud's phenomenon
-Nephritis is common cause of death in SLE (diffuse proliferative glomerulonephritis if nephritis & membranous glomerulonephritis if nephrotic)
-False + on syphilis test (RPR/VDRL) due to antiphospholipid ab, which cross-react cardiolipin used in tests
Labs: +ANA (sensitive, but not specific)
+anti-dsDNA (very specific, poor prognosis)
+anti-SM (very specific, not prognostic)
+antihistone ab (more sensitive for drug-induced lupus

Immunoglobuins, Malar rash, Discoid rash, Antinuclear Ab, Mucositis (oropharyngeal ulcers), Neurologic disorders, Serositis (pleuritis, pericarditis), Hematologic disorders, Arthritis, Renal Disorders, Photosensitivity (I'M DAMN SHARP)



-immune-mediated, widespread noncaseating granulomas & elevated serum ACE levels
-black females
-often asymptomatic except for enlarged lymph node, incidental findings on CXR of bilateral hilar adenopathy or reticular opacities
-associated with restrictive lung disease (interstitial fibrosis), erythema nodosum, Bell's palsy, epithelial granulomas containing microscopic Schaumann & asteroid bodies, uveitis, & hypercalcemia (due to elevated 1alpha-hydroxylase-mediated vit D activation in epithelioid macrophages)
Treatment: steroids


Polymyalgia Rheumatica

Symptoms: pain & stiffness in shoulders & hips, often with fever, malaise, weight loss, does not cause muscular weakness
-more common in women >50 yrs, associated with temporal (giant cell) arteritis
Findings: inc. ESR, normal CK
Treatment: Rapid response to low-dose corticosteroids



-most commonly seen in women 20-50 yrs.
-Chronic, widespread musculoskeletal pain associated with stiffness, parasthesia, poor sleep, & fatigue



-progressive symmetric proximal muscle weakness, characterized by endomysial inflammation with CD8+ T cells
-most often involves shoulders
Findings: inc. CK, positive ANA, + anti-Jo-1 ab
Treatment: steroids



-similar to polymyositis, but also involves malar rash (similar to SLE)
-Gottron's papules, heliotrope rash, "shawl & face" rash, "mechanic's hands"
-inc. risk of occult malignancy
-perimysial inflammation & atrophy with CD4+ T-cells
Findings: inc. CK, positive ANA, + anti-Jo-1 ab
Treatment: steroids


Myasthenia Gravis

-most common neuromuscular junction disease
-autoabs to postsynaptic ACh receptor
-Ptosis, diplopia, weakness, Worsens with muscle use
-Associated with Thymoma, thymic hyperplasia
-Give AChE inhibitor to reverse symptoms


Lambert-Eaton Myastheniac Syndrome

-uncommon neuromuscular junction disease
-autoabs to presynaptic Ca2+ channel, dec. ACh release
-proximal muscle weakness, improves with muscle use
-associated with small cell lung cancer
-no effect with AChE inhibitor administration


Myositis Ossificans

-Metaplasia of skeletal muscle to bone following muscular trauma
-Most often seen in upper or lower extremity
-May present as suspicious "mass" at site of known trauma or as incidental finding on radiography


Scleroderma (systemic sclerosis)

-Excessive fibrosis & collagen deposition throughout the body
-Commonly sclerosis of skin, manifesting as puffy & taut skin with absence of wrinkles
-Also sclerosis of renal, pulmonary (most likely cause of death), cardiovascular, & GI systems
-75% female
-Diffuse Scleroderma
-CREST Syndrome


Diffuse Scleroderma

-widespread skin involvement, rapid progression, early visceral involvement
-Associated with anti-Scl-70 ab (anti-DNA topo 1 antibody)


CREST Syndrome

-Raynaud's phenomenon
-Esophageal dysmotility
-Limited skin involvement , often confined to fingers & face, more benign clinical course
-Associated with anti-Centromere antibody



-Flat lesion with well-circuscribed change in skin color < 5mm
-Freckle, labile macule



-Macule > 5mm
-Large birthmark (congenital nevus)



-Elevated solid skin lesion < 5mm
-Mole (nevus), acne



Papule > 5mm



Small fluid-containing blister < 5mm
-chickenpox (varicella), shingles (zoster)



Large fluid-containing blister > 5mm
-Bullous pemphigoid



Vesicle containing pus
-Pustular psoriasis



Transient smooth papule or plaque
-Hives (urticaria)



Flaking off of stratum corneum
-Eczema, psoriasis, SCC



Dry exudate



inc. thickness of stratum corneum (psoriasis)



hyperkeratosis with retention of nuclei in stratum corneum (psoriasis)



Separation of epidermal cells (pemphigus vulgaris)



Epidermal hyperplasia (inc. spinosum)
(Acanthosis nigricans)



Inflammation of the skin (atopic dermatitis)



Pigmented Skin Disorders
-Normal melanocyte # with dec. melanin production due to dec. tyrosinase activity
-Can also be caused by failure of neural crest cell migration during development


Melasma (chloasma)

Pigmented Skin Disorders
-Hyperpigmentation associated with pregnancy "mask of pregnancy" or OCP use



Pigmented Skin Disorders
-Irregular areas of complete depigmentation
-Caused by a dec. in melanocytes



-Warts; caused by HPV
-Soft, tan-colored, cauliflower-like papules
-Epidermal hyperplasia, hyperkeratosis, koilocytosis
-Condyloma acuminatum on genitals


Melanocytic Nevus

-Common mole
-Benign, but melanoma can arise in congenital or atypical moles
-Intradermal nevi are papular
-Junctional nevi are flat macules



-Pruritic wheals that form after mast cell degranulation



-Normal # of melanocytes, inc. melanin pigment


Atopic Dermatitis (Eczema)

-Pruritic eruption, commonly on skin flexures
-Often associated with other atopic diseases (asthma, allergic rhinitis)
-Usually starts on the face in infancy & often appears in the antecubital fossae thereafter


Allergic Contact Dermatitis

-Type IV hypersensitivity rxn that follows exposure to allergen
-Lesions occur at site of contact (nickel, poison ivy, neomycin)



-Papules & plaques with silvery scaling, especially on knees & elbows
-Acanthosis with parakeratotic scaling (nuclei still in stratum corneum)
-Inc. stratum spinosum, dec. stratum granulosum
-Auspitz sign - pinpoint bleeding spots from exposure of dermal papillae when scales are scraped off
-Can be associated with nail pitting & psoriatic arthritis


Seborrheic Keratosis

-Flat, greasy, pigmented squamous epithelial proliferation with keratin-filled cysts (horn cysts)
-Looks "stuck on"
-Lesions occur on head, trunk, & extremities
-Common benign neoplasm of older persons
-Leser-Trelat sign: sudden appearance of multiple seborrheic keratosis, indicating on underlying malignancy (GI, lymphoid)


Pemphigus Vulgaris

Blistering Skin Disorders
-Potentially fatal autoimmune skin disorder with IgG ab against desmoglein 3 (1 &/or 3), a part of desmosomes (needed for cell adhesion)
-Immunofluorescence reveals abs around epidermal cells in a reticular or netlike pattern
-Acantholysis-intraepidermal bullae causing flaccid blister involving the skin & oral mucosa
- + Nikolsky's sign (separation of epidermis upon manual stroking of skin)


Bullous Pemphigoid

Blistering Skin Disorders
-Autoimmune disorder with IgG ab against hemidesmosomes (epidermal basement membrane, abs are "bullow" the epidermis), shows linear immunofluorescence
-Eosinophils within tense blisters
-Similar to but less severe than pemphigus vulgaris , affects skin but spares orla mucosa
-Negative Nikolsky's sign


Dermatitis Herpetiformis

Blistering Skin Disorders
-Pruritic papules, vesicles, & bullae
-Deposits of IgA at the tips of dermal papillae
-Associated with celiac disease


Erythema Multiforme

Blistering Skin Disorders
-Associated with infections (Mycoplasma pneumoniae, HSV), drugs (sulfa drugs, beta-lactams, phenytoin), cancers, & autoimmune disease
-Presents with multiple types of lesions (macules, papules, vesicles, target lesions-look like targets with multiple rings and a dusky center showing epithelial distuption)


Stevens-Johnson Syndrome

Blistering Skin Disorders
-fever, bulla formation, & necrosis, sloughing of skin, & a high mortality rate
-Typically 2 mucus membranes are involved & skin lesion may appear like targets as seen in erythema multiforme
-a more severe form with > 30% of the body surface area involved is toxic epidermal necrolysis


Acanthosis Nigricans

-Epidermal hyperplasia causing symmetrical, hyperpigmented, velvety thickening of skin, especially on neck or in axilla
-Associated with hyperinsulinemia (diabetes, obesity, Cushing's syndrome) & visceral malignancy


Actinic Keratosis

-Premalignant lesions caused by sun exposure
-Small, rough, erythematous or brownish papules or plaques
-Risk of squamous cell carcinoma is proportional to degree of epithelial dysplasia


Erythema Nodosum

-Inflammatory lesions of subcutaneous fat, usually on anterior shins
-Associated with sarcoidosis, coccidioidomycosis, histoplasmosis, TB, streptococcal infections, leprosy, & Crohn's disease


Lichen Planus

Pruritic, Purple, Polygonal Planar Papules an dPlaques are the 6 P's of lichen planus
-Sawtooth infiltrate of lymphocytes at dermal-epidermal junction
-Associated with hep C


Pityriasis Rosea

"Herald patch" followed days later by "Christmas tree" distribution
-Multiple plaques with collarette scale
-Self-resolving in 6-8 weeks



UV irradiation causes DNA mutations, inducing apoptosis of keratinocytes
-UVA is dominant in tanning and photoaging, UVB in sunburn
-Can lead to impetigo and skin cancers (basal cell carcinoma, squamous cel carcinoma, & melanoma)



-Very superficial skin infection
-Usually from S. aureus or S. pyogenes
-Highly contagious
-Honey-colored crusting
-Bullous impetigo has bullae & is usually caused by S. aureus



-Acute, painful, spreading infection of dermis & subcutaneous tissues
-Usually form S. pyogenes or S. aureus
-Often starts with a break in skin from trauma or another infection


Necrotizing Fasciitis

-Deeper tissue injury, usually from anarobic bacterial or S. pyogenes
-Results in crepitus from methane & CO2 production
-"Flesh-eating" bacteria
-Causes bullae & a purple color to the skin


Staphylococcal Scaled Skin Syndrome (SSSS)

-Exotoxin destroys keratinocyte attachment in the stratum granulosum only (vs. toxic epidermal necrolysis, which destroys the epidermal-dermal junction)
-fever & generalized erythematous rash with sloughing of the upper layers of the epidermis that heals completely
-Seen in newborns & children


Hairy Leukoplakia

-White, painless plaques on the tongue that can't be scraped off
-EBV mediated
-Occurs in HIV+ patients


Skin Cancer: Basal Cell Carcinoma:

-most common
-found in sun-exposed areas of body
-locally invasive, but almost never metastasizes
-Pink, pearly nodules, commonly with telangiectasias, rolled borders, & central crusting or ulceration
-BCCs also appear as nonhealing ulcers with infiltrating growth or as a scaling plaque (superficial BCC)
-"palisading" nuclei


Skin Cancer: Squamous Cell Carcinoma

-second most common skin cancer
-associated with excessive exposure to sunlight, immunosuppression, & occasionally arsenic exposure
-commonly appears on face, lower lip, ears, & hands
-locally invasive, but may spread to lymph nodes & will rarely metastasize
-Ulcerative red lesions with frequent scale
-Associated with chronic draining sinuses
-Histopathology: keratin "pearls"



-a varient of squamous cell carcinoma of the skin that grows rapidly (4-6 weeks) and may regress spontaneously over months


Skin Cancer: Melanoma

-common tumor with significant risk of metastasis
-S-100 tumor marker
-Associated with sunlight exposure; fair-skinned persons are at inc. risk
-Depth of tumor correlates with risk of metastasis
-Look for ABCDE: Asymmetry, Border irregularity, Color variation, Diameter (>6mm), Evolution over time
-At least 4 diff. types
-often driven by activation mutation in BRAF kinase
-Primary treatment is excision with appropriately wide margins
-Metastatic or unresectable melanoma in patients with BRAF V600E mutation may benefit from vemurafenif, a BRAF kinase inhibitor