Pathology of the Integumentary System, Pt. 3 Flashcards
What is perivascular dermatitis? Why is it considered nonspecific?
inflammatory cells aggregate around blood vessels
most common response to any injury —> aka superficial perivascular dermatitis, primarily hypersensitivity
What 4 common hypersensitivity disorders cause superficial perivascular dermatitis?
- atopic dermatitis
- cutaneous adverse food reaction
- flea bite hypersensitivity
- ectoparasitism
- histopathology not helpful for finding a cause
What are Type I hypersensitivities mediated by? How does it develop?
IgE
production of IgE causes the immediate release of vasoactive amines and other mediators from mast cells, which later recruits eosinophils
What is pruritus? How does it tend to manifest in dogs and cats? What are 5 common causes?
unpleasant sensation which provokes the desire to scratch (itching) —> mast cell aggregation
chewing, licking, scratching, rubbing, overgrooming
parasites, allergies, inflammation, neurogenic conditions, neoplasm
What is the difference between acute and chronic perivascular dermatitis gross presentation?
ACUTE: edema, erythematous papules, wheals
CHRONIC: alopecia, lichenification, hyperpigmentation
What is the difference between acute and chronic perivascular dermatitis histologically?
ACUTE: vascular dilation, dermal edema, spongiosis, perivascular eosinophils
CHRONIC: epidermal hyperplasia, compact hyperkeratosis, hyperplastic follicular infundibula, sebaceous gland hyperplasia, apocrine gland ectasia, fibrosis
What is utricaria/angioedema? What are 3 common causes? What is seen histologically?
(hives, heat bumps)
acute wheals, erythema, edema, and variable pruritus that typically only lasts 12-24 hours
- drugs
- venomous stings
- biological agents
no lesions or dermal edema
What is the most common cutaneous inflammatory and pruritic disease in dogs? What 3 breeds of dogs are most suscpetible?
canine atopic dermatitis
- terriers
- retrievers
- brachycephalic breeds
What is the typical age of onset of canine atopic dermatitis? How does it present?
1-3 years
generalized pruritis PRIOR to skin lesions
- seasonal***
- nonseasonal
- nonseasonal + seasonal worsening
What are the most common symptoms of canine atopic dermatitis after pruritus? Where on the body is it concentrated?
erythema, alopecia, excoriations, hyperpigmentation, lichenification
head, paws, flexor aspect of elbows, carpal and tarsal joints, axilla, groin, ventrum
Canine atopic dermatitis:
What secondary conditions are common with canine atopic dermatitis?
bacterial pyoderma and Malassezia dermatitis
What is thought to be the pathogenesis of canine atopic dermatitis? How is it diagnosed?
involves skin barrier dysfunction and dysregulated immune responses
diagnoses of exclusion —> allergy testing is only performed when the clinical diagnosis has been made by ruling out all other causes of pruritus/dermatitis
What is canine food allergy? What is the typical age of onset? What are common signs?
adverse reaction to a food or food additive
less than 1 year old
non-seasonal pruritus with variable response to steroids and possible GI signs
- secondary infection is common
How does canine food allergy typically present grossly?
same as atopic dermatitis - erythema, alopecia, excoriations, scales, crusts, hyperpigmentation, and lichenification on face pinnae, axillae, groin, paws, and perianal region
What is the pathogenesis of canine flea allergic dermatitis? Why is it considered seasonal? What is the common presentation and where on the body is it most common?
sensitization to flea saliva proteins through repeated and intermittent flea bites
based on flea activity
hypotrichosis, papules, erythematous plaques, and wheals concentrated on dorsal lumbar area, flanks, tail base, and hindlimbs
What is feline atopic skin syndrome (FASS)?
inflammatory and pruritic skin syndrome of cats manifested by a spectrum of reaction patterns, none of which are specific for this syndrome, and may be associated with IgE to environmental allergens
What are the 4 common cutaneous reaction pattern for FASS?
- miliary dermatitis (MD) - countless papules
- self-induced alopecia (SIA) - overgrooming
- face, head, neck pruritus (FHN)
- eosinophilic granuloma complex (EGC) - plaque
Miliary dermatitis:
cutaneous reaction pattern for FASS
Self-induced alopecia:
cutaneous reaction pattern for FASS
Face, head, neck pruritus:
cutaneous reaction pattern for FASS
Eosinophilic granuloma complex:
cutaneous reaction pattern for FASS
Miliary dermatitis (MD), histology:
What mite causes Sarcoptic mange in dogs? How is it classified and transmitted?
Sarcoptes scabiei var. canis
highly contagious, intensely pruritic
direct contact or via fomites
What kind of mites are Sarcoptes scabiei var. canis? How is it diagnosed?
burrowing mites —> live in tunnels burrowed into and under the stratum corneum
superficial skin scraping
- maculopapular eruptions
- crusting
- alopecia
What is seen histologically in Sarcoptic mange?
perivascular eosinophilic dermatitis with intralesional (under stratum corneum) arthropods
What causes cutaneous acariasis (mange) in cats, sheep/goats, rabbits, and cattle/horses?
CATS: Notoedres cati
SHEEP/GOATS: Psoroptes ovis
RABBITS: Psoroptes cunuculi
CATTLE/HORSES: Chorioptes bovis
What are 3 common secondary complicating factors to Sarcoptic mange?
- superficial trauma
- bacteria - Staphylococcus spp. (S. pseudintermedius)
- fungi - Malassezia pachydermatis
In what animals is Malassezia dermatitis most common? What causes it? What is it typically secondary to?
dogs - West Highland white terriers, dachshunds, English setters
Malassezia pachydermatis
underlying skin disease (atopy, food allergy)
What is typically seen grossly in Malassezia dermatitis? Where on the body is it most common? What condition is typically concurrent?
generalized alopecia, excoriations, erythema, scales —> lichenification
interdigital spaces, ventral neck axilla, perineal region, leg folds
otitis externa
What does Malassezia look like histologically?
footprints!
Malassezia dermatitis:
What is perivascular dermatitis with parakeratosis indicative of? What are 4 common conditions that cause this?
increased epidermal turnover
- trauma
- Malassezia infection
- zinc-responsive dermatosis
- superficial necrolytic dermatitis (hepatocutaneous syndrome)
What are the 2 types of zinc-responsive dermatosis?
TYPE I: more common inherited defect of zinc absorption or metabolism in Siberian Huskies and Alaskan Malamutes
TYPE II: more rarer condition found in any breed with a zinc deficient diet or one over-supplemented with chelating agents (calcium, phytates)
What presentation of zinc-responsive dermatosis is most common?
crusting, alopecia, scaling, and erythema on the face (muzzle, periocular region), mucocutaneous junctions, distal extremities, paw pads
What is seen histologically in zinc-responsive dermatosis?
When is zinc-responsive dermatosis common in pigs?
young pigs 2-4 months old not allowed access to soil or not supplemented with zinc
What is superficial necrolytic dermatitis? What animals is it most common in? What is it commonly associated with?
hyperkeratosis of the paw pad, bilaterally symmetrical erythema, scaling, crusting, erosions, and ulcers
small breed geriatric dogs
- liver disease, glucagonomas, diabetes mellitus (NOT interchangeable with hepatocutaneous syndrome)
- hypoaminoacidemia (depletion of aa necessary for skin health)
- hyperglucagonemia
What is the characteristic histology of superficial necrolytic dermatitis?
RWB
What is interface dermatitis? What is it usually caused by?
pathologic events that target basal keratinocytes and the dermoepidermal junction
immune dysregulation and autoimmunity
- Type III hypersensitivity: immune complex deposition (lupus erythematosus)
- Type IV hypersensitivity: autoreactive cytotoxic T cells (erythema multiforme)
What does interface dermatitis look like histologically?
How does interface dermatitis present grossly?
vesicles, erosions, ulcers
What type of disease is lupus erythematosus (LE)? What is the most common type?
autoimmune disease —> interface dermatitis
cuteaneous LE
- systemis is very rare
How does facial discoid lupus erythematosus (FDLE)? What dogs are more predisposed?
erythema, depigmentation, scales, crusts, erosions, and ulcers with atrophy and loss of the cobblestone appearance of the nasal planum
German shepherds
How should facial discoid lupus erythematosus (FDLE) lesions be prepared before biopsy?
treat with culture-based antibiotics, since it can look similar to mucocutaneous pyoderma
What are the 4 major histological features of facial discoid lupus erythematosus (FDLE)?
- lichenoid interface dermatitis: band of mononuclear cells infiltrate at the dermoepidermal junctions (lymphocytes)
- hydropic degeneration
- apoptosis of basal keratinocytes
- pigmentary incontinence
Facial discoid lupus erythematosus (FDLE):
How does interface dermatitis compare to lichenoid dermatitis?
INTERFACE: lymphocytic infiltrate at dermoepidermal junction WITH keratinocyte cell death (DLE)
LICHENOID: superficial diffuse dermatitis WITHOUT keratinocyte cell death (mucocutaneous pyoderma)
What is erythema multiforme? How does it present?
autoimmune disease caused by lymphocyte-mediated destruction of keratinocytes
erythematous macules, plaques, vesicles/bullae, ulcers, and crusts on the trunk, glabrous skin of the groin and axilla, and mucocutaneous junctions
What are the most commo causes of erythema multiforme?
- adverse drug reactions**
- neoplasia
- infection
- idiopathic
What is seen histologically in erythema multiforme?
lymphocytic interface dermatitis, transepidermal apoptotic keratinocytes, lymphocytic satellitosis
