PATHO 2 - INTEGUMENTARY SYSTEM

a) Macule

a circumscribed, area of discoloration (eg pigmentation, hemorrhage) up to 1 cm in diameter.

b) Patch

a macule over 1 cm in size.

c) Papule

a small (< 1 cm diameter) solid elevation of the skin.

d) Plaque

a larger, flat

e) Nodule

a circumscribed, solid elevation >1 cm in diameter that usually extends into the deeper layers.

f) Tumor

a large mass (neoplasia implied) that may involve any structure of the skin or subcutis.

g) Cyst

an epithelial lined cavity in the dermis or subcutis containing fluid or semisolid material.

h) Vesicle

a well circumscribed, < 1 cm diameter, elevation of the epidermis, filled with clear fluid.

i) Bulla

a vesicle (blister) > 1 cm diameter.

j) Pustule

a small, circumscribed, pus filled elevation of the epidermis.

k) Abscess

a well demarcated fluctuant lesion resulting from dermal or subcutaneous accumulation of pus.

l) Wheal

a sharply circumscribed, raised lesion due to dermal edema; will blanch with pressure.

a) Scale

an accumulation of loose fragments (flakes / dandruff) of cornified skin; can be primary (eg primary seborrhea) or secondary (eg chronic inflammation).

b) Crust

accumulation of dried material (eg exudate, blood /serum, scale, medication) on skin surface; can be primary (eg zinc responsive dermatosis) or secondary

c) Comedo

a hair follicle lumen plugged with cornified cells and sebaceous material; can be primary (eg Cushing’s disease) or secondary (eg demodecosis).

Alopecia

partial to complete loss of hair (baldness); can be primary (eg endocrine disease,follicular dysplasia) or secondary (eg with self

trauma or inflammation).

Hypotrichosis / atrichia

less hair than normal or absence of hair (ie failure to develop).

Effluvium / defluxion

excessive shedding or falling out of the hair.

Hypertrichosis (hirsutism)

excessive growth of hair.

Red (erythema)

pigmentation indicating inflammation / vasodilation

melanoderma (hypermelanosis) / melanotrichia

black pigmentation

leukoderma / leukotrichia / hereditary hypopigmentation (eg albinism)

white pigmentation

macular hemmorhage

red-purple-brown- black pigmentation

Icterus

yellow pigmentation

Cyanosis

Blue pigmentation

a) Epidermal collarette

a circular rim of keratin flakes following loss of the “roof”of a vesicle or pustule.

b) Erosion

a shallow epidermal defect that doesn't penetrate the basal laminar zone; heals without scarring.

c) Ulcer

a break in the epidermis with exposure of the underlying dermis; usually heals with a scar.

d) Excoriation

erosions or ulcers caused by scratching, biting or rubbing, usually due to pruritus.

e) Scar

an area of fibrous tissue that has replaced the damaged dermis and/or subcutis.

f) Fissure

a linear cleavage of usually thickened, inelastic skin.

g) Lichenification

a thickening and hardening of the skin with exaggeration of the superficial markings.

h) Callus

a thickened, rough, alopecic, lichenified plaque that develops on the skin.

a) Hyperkeratosis

increased thickness of stratum corneum

Orthokeratosis

increased thickness of stratum corneum, anucleated

Parakeratosis

Increased thickness of stratum corneum, nucleated

b) Epidermal hyperplasia (acanthosis)

increased thickness of the noncornified epidermis.

c) Epidermal atrophy

decreased thickness of the noncornified epidermis.

d) Intracellular edema

CELL DAMAGE leading to hydropic (vacuolar) or ballooning degeneration.

e) Intercellular edema (spongiosis)

accumulation of edema fluid in the intercellular spaces.

f) Acantholysis

loss of cohesion between epidermal cells leading to clefts, vesicles / bullae or pustules.

g) Exocytosis

migration of inflammatory cells through the intercellular spaces of the epidermis.

h) Pustule (microabscess)

microscopic or macroscopic cavities filled with inflammatory cells.

i) Crust

surface accumulations of varying combinations of keratin, serum, cell debris, bacteria, etc.

j) Necrosis / apoptosis

microscopic forms of keratinocyte death.

k) Dyskeratosis

premature or abnormal keratinization in the viable layers of the epidermis.

l) Hyper & hypopigmentation

excessive or decreased amounts of melanin within the epidermis

a) Dermal edema

see widened spaces between dermal collagen, perivascular edema or lymphatic dilation.

b) Collagen changes

including hyalinization, degeneration, mineralization, etc.

c) Fibroplasia / fibrosis / sclerosis

formation and maturation of fibrous tissue, leading to scarring.

d) Pigmentary incontinence

melanin granules free within the dermis or within dermal macrophages.

e) Follicular changes

include atrophy, dilation, keratosis, dysplasia, inflammation, etc.

f) Glandular changes

include inflammation, atrophy, hyperplasia, cystic change, etc.

g) Vascular changes

include fibrinoid degeneration, vasculitis, thromboembolism, etc.

Congenital hypotrichosis

Reported in all domestic species (variety of heritable syndromes in many breeds), but most common in calves.

Absence of hair follicles or abnormal follicular development (follicular dysplasia).

Hereditary collagen dysplasia

known by several names, ie Ehlers-Danlos syndrome, dermatosparaxis, cutaneous asthenia, etc.

is the most commonly recognized connective tissue disorder reported in humans and most domestic species.

Hereditary collagen dysplasia

results in hyperextensibility to skin that is easily torn with routine handling, play with littermates, scratching.

Hereditary Collagen Dysplasia

changes in dermis (eg thin, pale, haphazardly arranged collagen fibers) are seen in some

cases,

Mechanobullous disease / Epidermolysis bullosa

inherited structural defects in the basement membrane zone (BMZ) leads to blistering (bullae) and ulceration of the skin and mucus membranes.

epidermolysis bullosa simplex

defect in cytokeratins 5 & 14 of basal

cells

junction epidermolysis bullosa

defect in anchoring filament-hemidesmosome complexes

dystrophic epidermolysis bullosa

defect in anchoring fibrils

Sunburn and Solar Dermatosis / Dermatitis

• direct endothelial damage

• damage to keratinocytes with release of inflammatory mediators.

Photosensitization

• when photodynamic substances in skin are activated by UV-A (normally not harmful) or visible light.

• the absorbed energy creates free radicals which damage the skin.

Type I

Photosensitization via exogenous origin of photodynamic agents, especially certain plant toxins and drugs

Type II

photosesitization due to aberrant endogenous heme pigment synthesis, ie porphyrias

Type III (hepatogenous type)

photosensitization due to failure to remove phylloerythrin a photoreactive metabolite of chlorophyll

Type IV

Photosensitzation with unknown etiology / pathogenesis

Primary contact irritant dermatitis

skin contact by substances expected to cause irritation, ie

• caustic chemicals (eg acids, alkalies),

• concentrated drugs (eg insecticides),

• soaps/detergents,

• body excretions (eg anal sac, urine), etc.

Acral lick dermatitis

a relatively common psychogenic dermatitis of dogs, especially large active breeds and often young (< 5 yrs).

focal self-trauma, typically found on the dorsal surface of a distal

limb region.

acral lick dermatitis

usually results from boredom or anxiety

Feline psychogenic dermatitis

one cause of feline symmetric alopecia.

Contagious pustular dermatitis

common parapoxvirus infection (world wide distribution) in young sheep & goats.

Foot and Mouth Disease

Severe, highly contagious viral disease of livestock that has a significant economic impact.

Affects cattle, swine, sheep, goats and other cloven-hoofed ruminants.

Foot and Mouth Disease

caused by an Aphthovirus of the family Picornaviridae, seven strains (A, O, C, SAT1, SAT2, SAT3, and Asia1) are endemic in different countries worldwide.

Aphthovirus from Picornaviridae

Etiology of FMD

Foot and Mouth Disease

Lesions:

• Vesicles or blisters on the tongue, dental pad, gums, cheek, hard and soft

palate, lips, nostrils, muzzle, coronary bands, teats, udder, snout of pigs,

corium of dewclaws and interdigital spaces.

• Erosions on rumen pillars at post mortem. Gray or yellow streaking in the heart from degeneration and necrosis of the myocardium in young animals of all species (‘tiger heart’)

Fowl pox

A slow-spreading virus disease of chickens and turkeys

Fowl pox

Caused by an epitheliotropic DNA virus from the Avipox genus, the Poxviridae family.

G. Avipox, Poxviridae

Fowl pox etiology

Cutaneous form or dry pox

form of Fowl Pox characterized by development of proliferative lesions, ranging from small nodules to spherical warts

diphtheritic form (wet pox)

type of Fowl Pox characterized by slightly elevated white opaque nodules develop on the mucous membranes.

Diphtheric form

Which fowl pox form causes higher mortality rates, sometimes nearing 50% particularly in young birds.

Pyotraumatic dermatitis (“hot spots” or “acute moist dermatitis”)

a rapid onset superficial pyoderma due to intense pruritus (esp fleas; also other parasites, allergies, etc). Caused by self

Impetigo

a primary superficial pustular dermatitis that occurs mostly commonly in dogs (ie puppy pyoderma), especially due to coagulase

Coagulase positive Staphylococcus, ocassionally streptococcus

impetigo etiology

Skin fold pyoderma (Intertrigo)

predisposed by friction / moisture in skin folds, eg’s facial, lip, vulvar, tail

Papillomatous Digital Dermatitis (“hairy heel warts”)

initially an erosive / ulcerative plaque

Dermatophilosis (cutaneous streptothricosis, strawberry foot rot, rain scald, etc)

a superficial exudative dermatitis due to D. congolensis, especially ruminants & horses; rare in dogs, cats, etc. Seen worldwide, but most common in hot, humid regions with heavy rainfall.

Staphylococcal Folliculitis / Furunculosis

usually secondary to trauma; seen especially in saddle & tack areas. Typically see papules that may enlarge to nodules (~1cm) often with a central ulcer that can discharge exudate.

Staphylococcal Folliculitis / Furunculosis

also one cause of “pastern dermatitis”, a dermatitis affecting the caudal aspect of the pastern / fetlocks.

Pastern dermatitis

a dermatitis affecting the caudal aspect of the pastern / fetlocks.

Treponema spp

etiology of papillomatos digital dermatitis

Exudative Epidermitis (Greasy Pig Disease)

an acute, rapidly spreading, often fatal exudative superficial pyoderma seen in suckling to weaners (5

Diamond skin disease

lesions are the result of localized vasculitis and thrombosis.

Cutaneous (Superficial) Mycoses

restricted to keratinized tissues, ie stratum corneum, hair, nails.

Dermatophytosis

can see classical expanding circular patches of scaling / alopecia to papules / pustules / furunculosis / crusting. Due to infection with keratinophilic fungi (Microsporum and Trichophyton)

Malasseziasis

overgrowth of Malassezia pachydermatis, secondary to underlying skin disease, eg allergies, seborrhea, etc (similar to secondary pyoderma) grossly see erythema, alopecia, scale, greasy (rancid odor); if chronic see lichenification & hyperpigmentation.

Candidiasis

rare opportunistic skin infection, especially when immunocompromised or on long

Chytridiomycosis

cutaneous mycoses of frogs & salamanders