1
Q
Define acantholysis
A
- loss of cohesion b/t keratinocytes due to the breakdown of intercellular bridges
- can be due to immune destruction (i.e. pemphigus) or neutrophilic enzymatic destruction
- usually assoc. w/ formation of pustules, vesicles, bullae, or clefts
2
Q
Define acanthosis
A
- hyperplasia, thickening of the spinous cell layer (stratum spinosum) of the epidermis
- get rete ridge formation
- regular (even rete ridge size)
- irregular (uneven; more common)
- papillated (surface projections)
- pseudocarcinomatous (long, irregular, anastomosing rete ridges extending into dermis)
3
Q
What is alopecia?
A
hair loss
4
Q
What does anagen mean?
A
phase of hair cycle in which hair synthesis takes place
5
Q
What is anaplasia?
A
lack of cellular differentiation and organization, a feature of neoplastic cells
6
Q
Define angioedema
A
- vascular reaction involving the deep dermis or subcutis and consisting of edema manifested as giant wheals and caused by dilation and incr permeability of capillaries (deeper version of urticaria)
- often seen with Type I hypersensitivity reactions (insect bites, vax rxns, food allergy, atopy, drug reactions)
7
Q
What is ballooning degeneration?
A
- markedly swollen, eosinophilic keratinocytes usually in the more superficial layers of the epidermis
- most freq assoc. w/ viral infections
- can lead to vesicle formation
8
Q
Define carcinoma in situ
A
a malignant neoplasm of epithelial origin that has not invaded through the basement membrane
9
Q
Define catagen
A
transition phase of the hair cycle b/t growth and resting phases
10
Q
Define dermatophytosis
A
infection of the stratum corneum of the epidermis, hair or claws with fungi of the genera Microsporum, Epidermophyton, or Trichophyton
11
Q
What’s the difference b/t dermatitis and dermatosis?
A
- dermatitis = inflammation of the dermis
- dermatosis = noninflammatory lesion of the skin
12
Q
Define dyskeratosis
A
- premature keratinization of cells within the epidermis
- dyskeratotic cells are rounded up, hypereosinophilic and have nuclear degeneration
- common with parakeratosis and hyperplasia
13
Q
Define elastosis
A
degeneration of dermal CT leading to accumulation of elastotic fibers; sometimes seen with solar dermatitis
14
Q
Define epidermolysis
A
separation of the epidermis from the dermis
15
Q
Define excoriation
A
superificial loss of epidermal layers due to physical trauma (scratching)
16
Q
Define exogen
A
the stage of hair cycle where old hairs are shed
17
Q
Define furuncle
A
circumscribed, painful nodule (accumulation of pus) in the dermis secondary to follicular rupture
18
Q
Define furunculosis
A
- rupture of follicles usually due to inflammation, distension, and/or trauma leading to entry of follicular contents into the dermis
- seen most commonly with luminal folliculitis
19
Q
Define genodermatosis
A
genetically determined disorder of skin
20
Q
What is hydropic degeneration?
A
- intracellular fluid accumulation in cells of the basal layer or outer follicular root sheath and can result in the separation of the epidermis and dermis
- keratinocytes usually contain vacuoles
- seen with SLE, drug eruptions, dermatomyositis
21
Q
Define hyperkeratosis
A
- histologic term for thickening of stratum corneum; can occur secondary to trauma or inflammation or as a specific characteristic of certain diseases
- orthokeratotic or parakeratotic
22
Q
Define ichthyosis
A
congenital skin disorder in which the skin is thickened by scales (hyperkeratosis) that can crack into plates resembling fish scales
23
Q
Define impetigo
A
bacterial dermatitis characterized by pustules
24
Q
Define indurated
A
hardening of skin due to inflammation or fibrosis
25
Define interface
inflammation arranged in a layer close to and often obscuring the epidermal-dermal junction (interface), and with vacuolated (hydropic degeneration) and sometimes apoptotic basal cells; can be mild (cell poor) or extensive (cell rich)
26
Define intertrigo
dermatitis that develops b/c of friction b/t apposing skin surfaces (e.g. adjacent folds)
27
Define keratinocytes
the epidermal cells that synthesize keratin and comprise more than 90% of epidermal cells
28
What are Langerhans' cells?
intraepidermal dendritic antigen-presenting cells
29
Define lichenification
thickening of skin with accentuation of skin creases due to marked acanthosis
30
Define macule
flat, circumscribed lesion of altered skin color
31
What is a Merkel cell?
a neuroendocrine cell found in the stratum basale
32
What is panniculitis?
* inflammation of subcutaneous adipose tissue
33
What is parakeratosis/parakeratotic hyperkeratosis?
* thickening of stratum corneum with retention of nuclei
* indicates **cornification process is abnormal**
* e.g. superficial necrolytic dermatitis, Zn responsive dermatosis
34
What are Pautrier's microabscesses?
a localized intraepidermal collection of neoplastic lymphocytes characteristic of epitheliotrophic lymphoma (mycosis fungoides)
35
What is pemphigus?
a group of cutaneous diseases associated with blistering
36
Define pigmentary incontinence
melanin pigment within dermal macrophages or free in the dermis developing via injury to pigment containing basal layer cells
37
What is seborrhea?
nonspecific term for clinical signs of scaling, crusting, and greasiness. Primary seborrhea is a more specific term applied to cornification disorders
38
What is spongiosis?
* **intercellular edema** which, by widening of the intercellular space and stretching of the intercellular bridges, creates a spongelike appearance of the epidermis
* seen with inflammation, contact irritant dermatitis, feline eosinophilic plaques
* severe spongiosis can lead to vesicle formation
39
What is telogen?
resting phase of the hair cycle
40
What is urticaria?
usually transient vascular reaction in the **upper dermis** consisting of edema manifested clinically as wheals (hives); a more superfical version of angioedema
41
What is vitiligo?
direct damage to melanocytes due to immunogens on the surface of these cells
42
What is orthokeratotic hyperkeratosis?
* buildup of excess keratin after **normal cornification has occurred** (cells **have lost their nuclei)**
* can be d/t excess production or lack of exfoliation of keratin
* can be loosely arranged (endocrine dermatosis) or compact (chronic trauma)
43
What is hypergranulosis?
* increase in width of stratum granulosum, incr in cells with keratohyalin granules
* lack of stratum granulosum in a hyperplastic epidermis may indicate incr epidermal turnover time w/ altered differentiation
44
Define apoptosis
* programmed cell death
* usually seen in basal layer but can become transepidermal in some dz states
* apoptotic keratinocytes resemble dyskeratotic keratinocytes and are shrunken and hypereosinophilic
* often seen with immune mediated dz; e.g. systemic lupus erythematosus, erythema multiforme
45
What are potential causes of epidermal necrosis?
* physical injury, chemical exposure, ischemia, adverse drug reactions
* injured cells release contents into extracellular space and incite inflammation
46
Describe atrophy
* thinning of the epidermis due to decr in # and size of cells of the epidermis
* **consequence of sublethal injury**
* most common cause: endocrine dermatoses, but can occur w/ partial ischemia, malnutrition
47
What is intrakeratinocyte fluid accumulation typically seen with and what does the skin look like histologically?
* superficial necrolytic dermatitis
* cells appear enlarged and are pale staining
48
What are clefts?
empty slit like spaces in the epidermis or at the epidermal/dermal junction; form from mechanisms similar to vesicles
49
What is exocytosis?
* **migration of leukocytes or RBCs into the epidermis**; if keratinocytes are damaged, they release cytokines that recruit inflamm cells
* Neutrophils: nonspecific, common w/ bacterial dz
* Eosinophils: allergic dz, ectoparasites
* Lymphocytes: immune mediated, ectoparasites, atopy, seborrhea, mycosis fungoides
50
What is hyperpigmentation?
* incr in melanin in the epidermis and possibly in dermal melanophages; non specific change that occurs in any chronic dermatitis
51
What are lentigines?
focal areas of hyperpigmentation that correspond to melanocyte hyperplasia; common in cream, orange, tricolored cats, rare in dogs
52
What is hypopigmentation?
* most often acquired d/t damage to melanocytes and adjacent keratinocytes or basal layer --\> leads to pigmentary incontinence
* seen with SLE, drug eruptions, pemphigus, mycosis fungoides, vitiligo
* **very characteristic of uveodermatologic syndrome**
53
What are the definitions of leukoderma and leukotrichia?
* decr pigmentation of skin and hair, respectively
54
What is follicular hyperkeratosis seen with?
* primary seborrhea, vitamin A responsive dermatosis, and endocrine dermatoses
55
What is follicular atrophy?
* shrinking of hair follicles typically seen in endocrinopathies, ischemia, traction (tight bows on Yorkies); may also occur as a physiologic process related to normal cyclic changes
56
What is follicular dysplasia?
* abnormal development of hair follicle that leads to alopecia
* most associated with uncommon coat colors (blue, fawn) --\> Color Mutant Alopecia
57
Define folliculitis
* hair follicles are the primary focus of the inflammatory infiltrate
* **luminal**: inflamm within lumen of follicle; e.g. bacterial (Staph), fungal (dermatophytosis), or parasitic dz (demodicosis)
* **mural**: leukocytes target the wall; e.g. feline mosquito bite hypersensitivity
* **bulbar**: e.g. alopecia areata
58
What are the various layers of the epidermis and what are specific characteristics of each?
* **Stratum corneum -** mostly dead, fully keratinized cells, flattened, most superficial
* **Stratum lucidum -** *only present in non-haired skin* - composed of compact fully keratinized cells
* **Stratum granulosum -** dying cells, contain keratohyalin granules
* **Stratum spinosum -** polyhedral shape, prominent intercelluar bridges, growing/synthesizing keratin
* **Stratum basale -** germinal layer - gives rise to the above layers
* **Basement membrane -** barrier b/t epidermis and dermis, anchors cells
59
What are considered adnexa?
* hair follicles
* sweat glands (apocrine, eccrine on footpads)
* sebaceous glands (holocrine)
* mammary glands
60
What is the difference between a primary and secondary lesion?
* Primary - the initial lesion, most representative of the underlying etiology and are most useful for evaluation
* Secondary - evolutionary lesions
61
What are causes of sebaceous gland hyperplasia?
chronic inflammation, seborrhea, aging change
62
What are causes of sebaceous gland atrophy?
* endocrine dermatoses, aging, end result of severe chronic inflammation of glands (i.e. sebaceous adentitis)
63
Define sebaceous adenitis
* inflammation that targets sebaceous glands and can lead to their complete destruction resulting in severe hyperkeratosis
* often seen with folliculitis, demodicosis
64
Describe fibrosis
* increase in collagen and fibroblasts (spec. in dermis), the end result of tissue repair that may be preceded by formation of granulation tissue, essentially a scar
* may be secondary to chronic trauma, inflammation
65
Define collagen degeneration or collagenolysis
* collagen can become granular and fragmented and have altered staining qualities such as incr eosinophilia/basophilia
* "flame figures" - granular eosinophilic debris on and around collagen seen w/ dz w/ eosinophilic infiltrates (mast cell tumors, arthropod bites)
66
What causes collagen mineralization?
* most often a form of **dystrophic** mineralization seen in Cushing's dz; can be **metastatic** as in Vit D/Ca/Phos imbalance, some **idiopathic** cases
67
What occurs with collagen atrophy?
* decr in size of collagen bundles most commonly seen in a Cushingoid cat
* entire dermis is thinner than normal, very fragile, and easily torn
68
What happens with collagen dysplasia?
* abnormally formed collagen found in certain inherited metabolic conditions
* has decr tensile strength and incr distensibility leading to freq tears and non-healing wounds
69
Define solar elastosis
* incr in production of elastin by fibroblasts that are not functioning normally as a result of chronic actinic damage; often seen along with sun-induced SCC
* most common in the horse
70
What is mucinosis?
* incr in glycosaminoglycans that trap water leading to myxedema and separation of collagen bundles, leads to a puffy look of the skin
* can form vesicles if severe
* normal in Shar Peis
* often seen in hypothyroidism and lupus erythematosus
71
What is fat necrosis?
* may occur anytime there is inflammation, necrotic fat often seen in cases of atypical mycobacteriosis of cats
* damaged adipocytes release lipid into areas of inflammation
* can also see in lupus and rabies vax rxns, trauma to panniculus, or pancreatitis
72
Describe vasculitis
* dermal vessels targeted by inflammation - mural infiltrates of neutrophils, fragmentation of PMNs, fibrinoid necrosis of vessel wall
* may see ulceration or sloughing of extremities
* usually a feature of Type III hypersensitivity rxns (immune complex dz)
* e.g. SLE, septicemia, DIC, toxins, frostbite, cold agglutinin dz
73
When should you biopsy?
* in the face of devastating dz
* when a neoplastic process is possible
* when the condition is longstanding and tx have failed
* when you have little to no idea what the dz process is
74
What do you biopsy?
* select multiple cutaneous sites representative of the range of lesions present
* look for fully developed primary lesions (e.g. vesicles, pustules, papules)
* if not evident, select secondary lesions and be sure to **include crusts, leading margins, and edges of ulcerated lesions**
75
What disease pattern might you expect to see with a particular cellular infiltrate?
* Neutrophils - active inflammation, e.g. folliculitis due to parasites, dermatophytes, or bacteria
* Eosinophils - ectoparasitism or allergic dz, furunculosis
* Mononuclear phagocytes - ticks, viruses, cell-mediated immune response, persistent antigen in tissues stimulating cell-mediated immunity
* Lymphocytes and plasma cells - (present in normal skin), local or systemic antigenic stimulation
* Mast cells - (present in normal skin), IgE mediated hypersensitivity, cell mediated type IV hypersensitivity
76
Describe perivascular dermatitis. What are some conditions suggested by this disease pattern?
* Pathogenesis - most common pattern, not specifc for any one dz, but **most often suggestive of hypersensitivity rxn**
* Conditions suggested:
* w/ irregular epidermal hyperplasia
* acral lick dermatitis, flea bite hypersens, sarcoptic mange, atopic dermatitis
* w/ orthokeratotic hyperkeratosis
* seborrhea, ichthyosis
* w/ parakeratotic hyperkeratotis
* Zn responsive dermatitis, malassezia dermatitis
* w/ marked epidermal spongiosis
* feline eosinophilic plaque, miliary dermatitis
* w/ severe ulceration
* physicochemical injury: photosensitization, hot spots
77
Describe interface dermatitis. What are some conditions suggested by this disease pattern?
* hydropic degeneration and apoptosis in basal layer of epidermis accompanied by bands of lymphocytes, plasma cells, +/- macrophages at dermal/epidermal junction; pigmentary incontinence
* may see **depigmentation, thickening of epidermis, erosions, or ulcerations**
* Pathogenesis: damage to basal cell layer of epidermis, often involves T-cell attack
* Conditions suggested:
* Cell poor: familial canine dermatomyositis, toxic epidermal necrolysis
* Lymphoplasmacytic - erythema multiforme, SLE
* Lymphohistiocytic - uveodermatologic (VHK) syndrome
78
Describe vasculitis. What are some conditions suggested by this disease pattern?
* leukocytes within walls of arterioles or venules, possible fibrinoid necrosis
* Gross lesions = edema, cutaneous hemorrhage, infarction, sloughing of extremities, ulcers, atrophic dermatitis
* Pathogenesis:
1. **immune mediated Type II hypersensitivity (ab/ag complex deposition)**
2. **primary bacterial dz**
3. **bacterial septicemia/systemic infxn**
* Conditions suggested: SLE (1), eriselothrix rhusiopathiae septicemia (3), rickettsia rickettsi (3), idiopathic
79
Describe nodular to diffuse dermatitis. What are some conditions suggested by this disease pattern?
* dermis and possibly panniculus have nodules, sheets or diffuse infiltrates of inflamm cells (typically granulomatous to pyogranulomatous)
* Gross lesions: multiple papules and nodules that may coalesce, ulcerate, and drain
* Pathogenesis: persistent Ag stim inciting a CMI response, may be infectious or noninfectious
* Conditions suggested:
* Infectious: pathogenic/opportunistic fungi, bacterial granulomas, Leishmania, Pythium (oomycetes), algae
* Non-infectious: FBs
* Idiopathic: cutaneous reactive histiocytosis, idiopathic sterile nodular dermatosis
* Eosinophilis = linear granulomas in cats
* Neutrophilic = deep pyodermas, abscesses
80
Describe vesicular or pustular patterns. What are some conditions suggested by this disease pattern?
* gross lesions: primary lesions = **vesicles, pustules, or bullae**, secondary lesions = **erosions, ulcers, crusts**
* **Intraepidermal- suggested conditions**
* ****_subcorneal vesicle/pustule_: superficial pyodermas (PMNs), pemphigus foliaceus (PMS, EOS), SLE - feline (PMNs), ectoparasites/allergies (EOS)
* _suprabasilar acantholysis_: pemphigus vulgaris (separation just above basal layer, "tombstones")
* **Subepidermal -** entire epidermis is separated from the dermis
* Pathogenesis: immune mediated and enzymatic destruction of basement membrane; genetic defects in structural components of BM, physical damage of BM
* Suggested conditions: severe lichenoid dermatosis (SLE), mechanobullous dz, thermal burns, TEN, bullous pemphigoid
81
Describe the patterns of folliculitis and furunculosis. What are some conditions suggested by this disease pattern?
* inflammation targets some part of follicles or sebaceous glands; furunculosis occurs once follicular wall is destroyed by infiltrate, releasing contents into the dermis
* grossly: follicular papules or nodules and patchy alopecia, ulcerated/draining lesions if severe
* Pathogenesis: colonization/infestation of hair follicles by bacteria, parasites, or fungi; could be immune mediated or idiopathic
* Suggested conditions:
* _demodicosis (PMNs or lymphs)_
* _bacterial (staph) infxs (PMNs)_
* _dermatophyte infections_
* _feline acne (PMNs)_
* pelodera infxns
* arthropod bites
* alopecia areata (lymphocytic bulbar folliculitis)
* eosinophilic mural folliculitis
82
Describe panniculitis. What are some conditions suggested by this disease pattern?
* inflammation targets the subcutaneous tissues
* grossly: variably sized papules and nodules that may ulcerate and drain an oily substance
* pathogenesis: infectious agents, may be traumatic implantation or part of systemic disease, many sterile or idiopathic
* suggested conditions:
* atypical mycobacteriosis (cats)
* nocardia
* FBs
* idiopathic
* vaccine induced - lymphocytic
* feline nutritional pansteatitis
* feline dermatophytic mycetomas (Persians)
83
Describe atrophic dermatoses. What are some conditions suggested by this disease pattern?
* epidermal and follicular atrophy w/ orthokeratotic hyperkeratosis; follicles in telogen or catagen, sebaceous gland and dermal atrophy, **hyperpigmentation of the epidermis**
* grossly: lesions are bilateral and symmetrical hypotrichosis, thin, often translucent skin with comedones and possible telangiectasia and hyperpigmentation (if d/t systemic condition)
* pathogenesis: **most common is a hormonal imbalance** leading to altered microenvironment and failure of appropriate stimulus for maintenance of skin components, genetic defects
* Suggested conditions:
* Hyperadrenocorticism
* Hypothyroidism
* Sex hormone related dermatoses
* Dermatospraxis
* Ischemia
* **Feline psychogenic alopecia**
* **Color mutant alopecia**
* **Feline paraneoplastic alopecia**
Systemic Pathology
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