L2-Physical/ Chemical injury, nutritional endocrine and hypsensitivity disorders Flashcards
Pyotraumatic dermatitis
hot spot- physical injury
-complication of allergic dermatitis
-breeds with thick undercoat are predisposed
CONSTANT SELF TRAUMA, PAINFUL LESIONS
sharply demarcated areas of alopecia with exudate and ulceration
injection site reaction
due to REACTION TO ADJUVANT (RABIES)
dermal nodule
Psychogenic alopecia
cats, exacerbated by stress
Acral lick dermatits
lick granuloma-dogs
large active-breed dogs
persistant licking and chewing
distal extremities
Thermal injury
liquids, fire, electrical wires, hot metals, hot blankets, lightning strike
can take time to fully see lesion extent 24-48hrs
Death often due to severe protein/fluid loss and secondary infections
dry heat- desiccation
moist heat- boiling and coagulation
First degree thermal injury
only involve epidermis no vesicles or blisters, erythematous area
second degree thermal injury
epidermis, superficial dermis affected
vesicles and bulla in epidermis
third degree thermal injury
full thickness through epidermis and dermis
coagulative necrosis, thrombosis of vessels
Fourth degree thermal injury
similar to third degree, but penetrates into subQ tissues and beyond
Thermal injury classification
Radiation acute injury
damage to rapidly dividing cells
lesions appear 2-4 weeks after exposure
erythema, edema- desquamation
alopecia due to damage to hair follicles
sebaceous glands damaged- will have scaling
Chronic radiation injury
months to years after treatment
damage to microvasculature
thin epidermis, hyperkeratosis and hyperpigmentation, chronic ulcers may devlop
dermis thickened with fibrosis
primary contact dermatitis
contact with substance that causes direct damage
does not involve prior sensitization
erythema, swelling, papules- location depends on toxin application
venom- spiders, snakes, bees, wasps
swelling/ edema, hemorrhage, necrosis, sloughing of tissue
brown recluse spider- dermonecrosis and eschar formation
snakes- crotalines- rattlesnakes, copperheads, cottonmouths, have most toxic venom
head and legs usually affected
mineralization in tissues
Dystrophic
secondary to injury, inflammation, degeneration
often localized
mineralization in tissues/Metastatic
secondary to systemic calcium/ phosphorus disturbance
chronic renal failure, hyperparathyroidism, hypercalcemia of malignancy
multiple tissues can be effected
Cutaneous mineralization
Calcinosis cutis
dystrophic mineral
associated with hyperadrenocorticism or cushings disease
mineral within dermis
Calcinosis circumscripta
tumoral calcinosis-pathogenesis unknown
large breed, young dogs, GSD predisposed
skin over bony prominences
bulging mass, contains chalky white material in deep dermis
Heavy metal toxicity/Thallium toxicity
similar pharmacologic actions to lead and mercury
acute exposure- severe GI irritation, motor issues
chronic exposure- marked erythema, scaling, alopecia, crusting
start at commissures of lips and expand over head and face
massive parakeratotic hyperkeratosis
diagnostic sampling- thalium in urine or stomach contents
Heavy metal toxicity/Selenium
occurs in grazing animals- skin lesions can take months to devlop
ingestion of selenium-accumulating plants- astragalus oxytropis
history of new herds to field with toxic plants, or fields with very little feeds
cattle and horses- alopecia, rough hair coat
lose hairs of mane and tail
hooves- coronary band lesions, dystrophic grooves, cracks, corrugations parallel to coronary band
Mycotoxicosis/Ergotism
-claviceps purpurea in seeds of grasses and grains
-toxic alkaloids cause diseases
Mycotoxicosis/Fescue
Tall fescue grass with fungus Neotyphodium coenophialum
- Toxic alkaloids cause disease not the fungus itself
- most common in cattle
MARKED PERIPHERAL VASOCONSTRICTION
thrombosis and ischemic necrosis of tissues
Distal extremities
can lead to SLOUGHING OF HOOVES
Hairy Vetch toxicity
VISCIA VILLOSA ROTH
-legume often found in feed or pasture
-not all animals with have clinical signs
- likely due to prussic acid, but unknown pathogenesis
3 syndromes
- acute neurologic-fatal
systemic disease- subQ swelling, bronchitis-fatal
SYSTEMIC GRANULOMATOUS DISEASE- most common crusting, alopecia, lichenification/thickening, pruritic
Biopsy- DX of exlusion
rule out fungal, mycobacterium
Actinic or solar dermatitis
- sunburn
- mainly in cats, dogs, pig, cows and goats
LIGHT COLORED ANIMALS - cats/ white- blue eyed animals
tips of ears, nose, eyelids, lips - erythema, crusting, alopecia
- CAN PROGRESS TO SQUAMOUS CELL CARCINOMA
photosensitization
- occurs when PHOTODYNAMIC PIGMENTS ARE DEPOSITED IN SUNLIGHT-EXPOSED SKIN
- plant pigments, drugs, byproducts of hemoglobin metabolism, chlorophyll degradation products
- pigments usually ingested from plants
- see lesions in grazing animals
LESIONS ON SKIN EXPOSED TO SUN, ESPECIALLY LIGHT- COLORED SKIN
erythema, edema, exudate, necrosis, sloughing - very pruritic
Photosensitization types
type I: direct ingestion ( primary hypersensitivity) of plants with pigments- st. johns wort and buckwheat, moldy cooperia- hill country rain lilly
type II: defective heme synthesis- rbc production
- uroporphyrin by- product accumulation
- congenital defect- causes porphyria- not common
type III: damaged liver- most common- ingest plant plus liver damage
most common form in domestic species
damaged liver- unable to secrete phylloerthrin
toxic plants: lantana, trifolium, panicum grass
ENDOCRINE: general lesions with endocrine disease
skin manifestations not unique to on specific disease
include BILATERALLY SYMMETRICAL ALOPECIA
dry, dull, brittle hair coat
hyperpigmentation
endocrine/Hypothyroidism
most common endocrinopathy in dogs
usually middle aged dogs
thyroid hormone TH needed for hair follicle growth, regulates sebum from sebocytes
seborrhea, dry brittle hair, hyperpigmentation, comedones
bilaterally symmetrical alopecia
elbows, hocks, hips, neck ( collar) entire tail
diagnostics: low T4, low free T4, high TSH
endocrine/ hyperadrenocorticism
cushings disease
middle aged to older dogs
due to tumor in pituitary gland, tumor in adrenal gland, iatrogenic
BILATERALLY SYMMETRICAL ALOPECIA ALONG TRUNK, THIN PENDULOUS ABDOMEN, hyperpigmtation
calcinosis cutis
diagnostics: ACTH stim or LDDS test
endocrine/ PPID
pituitary pars intermedia dysfunction
- horses
due to tumor in the pituitary gland
coarse, long shaggy hair coat that doesnt shed (hirsutism), sweating
also associated with laminitis and rotation of P3
endocrine/ hyperestrogenism
excess estrogen production
dogs: male dogs with sertoli cell tumor
female with ovarian neoplasms or pcos
symmetrical alopecia
perineum and genital region- trunk
Ferret- associated with adrenal tumor
bilateral symmetric alopecia
vulvar enlargement
endocrine/ alopecia X
dogs- usually plush- coated breeds
pomeranians, husky, malamute, chows
normal thyroid and adrenal function- unknown pathogenesis
symmetrical alopecia of trunk, caudal thighs, perineum, neck ( head and limbs not involved)
hyperpigmentation of exposed skin
NON- PRURITIC
endocrine/ canine recurrent flank alopecia
usually short coated dog breeds- boxers, bulldogs
bilaterally symmetrical alopecia of the flank
very well demarcated, underlying skin usually hyper pigmented
recurrent or seasonal
NON PRURITIC
hypersensitivity/ Type I
Type I: immediate, targets allergens, anaphylaxis
vascular dilation, edema, inflammation
hypersensitivity/ Type II
Type II: antibody mediated, targets cellular antigens
- cell lysis and inflammation
hypersensitivity/ TYPE III
Type III
immune complex mediated, targets soluble antigens vasculitis, inflammation
hypersensitivity/ Type IV
TYPE IV: DELAYED. cell mediated T, targets about any antigen
edema, cell lysis, granulomas
Atopic dermatitis
allergic skin disease- inflammatory and pruritic
common in dogs
young dogs less than 3 yr old
can occur in cats
main clinical sign is (PRURITUS)
may be seasonal and progress to year round
responds excellent to steriods
Atopic dermatitis
5 Fs: face, feet, folds, flexures, friction
diagnosis: young dog, indoor living, pruritus prior to lesions, front paws and inner pinna affected
rule out FAD and other mites
PRURITUS AND ERYTHEMA
excoriations, ulceration, papules
due to self trauma
can lead to hot spots
cutaneous adverse food reaction
occurs in dogs, rarer in cats
allergen: food protein- beef, chicken, milk, eggs, wheat
nonseasonal pruritus
tends to respond poorly to steriods
distribution very similar to atopic dermatitis
5 Fs: face, feet, fold, flexures, friction
diagnostic: food trial
Urticaria
hives/wheals, heat bumps
very common in horses
last up to 24 hours, then go away
lots of causes:
food, drugs, insect bites, contact allergens, infections
increased vascular permeability from histamine- edema leaks out
discrete, well circumscribes, edematous, plaques with flat top
insect hypersensitvity
venom, saliva, skin, capsule, feces
tend to be seasonal
pruritic papules with crusting, thinly haired areas more effected
flea allergy dermatitis: ctenocephalides felis
most common allergic dermatosis of dogs and cats
alopecia, lichenification, hyperpigmentation over RUMP AND CAUDAL THIGHS
very pruritic- often have self trauma
in cats, miliary dermatitis with small papules
Insect hypersensitivity
Culicoides: hypersensitivity in horses
most common allergy
queensland itch, summer itch, summer eczema
very pruritic- head, neck, ears, back and tailhead
papules that can becomes excoriations, crust, alopecia
