Pathology of the Integumentary System, Pt. 4 Flashcards
How do acantholytic cells compare to macrophages?
ACANTHOLYTIC: loss of coherence between epidermal cells due to the breakdown of intercellular bridges
MACROPHAGES: phagocytic vacuoles
What is the most common cause of intraepidermal vessicular/pustular dermatitis?
acantholysis - loss of cohesion between keratinocytes resulting in the breakdown of the intracellular bridges (desmosomes)
What are the 2 features of acantholysis?
- formation of clefts, vesicles, pustules
- acantholytic cells: keratinocytes that separate completely from their neighbors, become round, with a round nucleus and eosinophilic cytoplasm
How does intraepidermal vesicular/pustular dermatitis progress?
transient, vesicles/bullae and pustules —> erosions, crusts
What are 3 causes of acantholysis?
- Pemphigus foliaceous - antibodies against desmocolin-1 in the desmosomes
- bacteria - Staph. pseudintermedius releases exotoxins
- dermatophyte - fungi release proteolytic enzymes
How does pemphigus foliaceous, pemphigus vulgaris, and subepidermal blistering disease clefts compare?
PF: subcorneal
PV: suprabasal
SBD: subepidermal (subbasal)
What causes pemphigus foliaceus? What type of hypersensitivity is this?
production of autoantibodies against desmocolin-1
Type II —> Ab-mediated
How does pemphigus foliaceus present? In what dogs is it most common? What needs to be ruled out before diagnosis?
pustules, erosions, and crusting on the face (+nasal planum), ears, and paw pads
middle-ages dogs
infections by bacteria and dermatophytes (culture, treat, see if lesions disappear)
What is seen on cytology and histology in pemphigus foliaceous?
CYTO: numerous neutrophils with acantholytic cells
HISTO: superficial intraepidermal (subcorneal) pustular dermatitis with acantholytic cells
Feline pemphigus foliaceus:
How does pemphigus vulgaris present? What is its cause?
vesicles and bullae —-> erosions and ulcers in the oral cavity, mucocutaneous junctions, and skin
- most common in middle-aged dogs
production of an autoantibody against desmoglein-3
What is seen histologically in pemphigus vulgaris?
acantholysis with suprabasilar clefting that look like a row of tombstones
Why do the vesicles at different places in pemphigus foliaceus and vulgaris?
PF - DSC-1 is present in keratinocytes of canine footpad and interfollicular epidermis, but not detected in the buccal mucosa
PV - DSG-3 is restricted to the basal and lower stratum spinosum on the footpad, haired skin, and buccal mucosa
What allows for bacterial infections due to normal commensal organisms?
skin barrier damage or immune deficiency (usually Staphylococcus pseudintermedius in dogs - canine pyoderma)
What is impetigo? What is a major predisposing factor? What microorganism causes this?
puppy pyoderma with pustules not associated with hair follicles on the sparsely haired area like ventral abdomen, perineum
cutaneous abrasions, immunosuppression caused by a newly developing immune system
Staphylococcus pseudintermedius
What is seen histologically in impetigo?
subcorneal pustules with bacteria +/- acantholysis
Impetigo, cytology:
What is dermatophytosis? How is it visualized histologically?
infection due to fungi, characterized by neutrophil accumulation and pustule formation
GMS silver stain that makes fungi stain black
What causes porcine exudative epidermitis?
(greasy pig disease)
Staphylococcus hyicus infection that produces exotoxins that causes intraepidermal cleavage and pustule/crust formation
What causes dermatophilosis? Where/in what animals is it most common?
(rain rot)
Dermatophilus congolensis
cattle, goats, sheep, and horses in hot and humid areas with heavy rainfall
What are 2 critical factors that can lead dermatophilosis? How does it prevent?
- skin trauma
- prolonged moisture
thick, yellow-brown keratinized crust on any area of the body
What are the 2 causes of subepidermal vesicular dermatitis?
(subepidermal blistering disease)
- congenital defect in structural proteins of BM zone and cytoskeleton of basal keratinocytes (epidermolysis bullosa)
- autoantibody targeting antigens of the BM protein (epidermolysis bullosa aquisita, bullous pemphigoid, mucous membrane pemphigoid)
What is the general prognosis of diseases with subepidermal vesicular dermatitis?
poor prognosis —> difficult to treat
What is a major histology characteristic of subepidermal vesicular dermatitis?
What are the gross lesions associated with subepidermal vesicular dermatitis?
vesicles —> ulcers
What causes congenital epidermolysis bullosa? How does it present?
(aplasia cutis congenita, epitheliogenesis imperfecta)
congenital defect in structural proteins of the BM zone and cytoskeleton of basal keratinocytes
vesicles/bullae, erosions, ulcers, and sloughing skin, nails, or hooves (skin, oral cavity, extremities, paw pads
How does mucous membrane pemphigoid (MMP) present? What makes it unique compared to other subepidermal vesicular diseases? What dogs are predisposed?
ulcers in the oral cavity, nasal region, periocular region, and genital region (no paw pad!)
has a better prognosis
German shepherds (aquired)
What is perifolliculitits? Luminal folliculitis? Mural folliculitis, furunculosis?
inflammation around the hair follicle
inflammation of the lumen of the hair follicle
inflammation of the wall of the outer sheath
follicle rupture with inflammation
Furunculosis:
How does folliculitis present?
papules, pustules, and alopecia that elevate hair follicles
What are the 3 major causes of folliculitis?
- bacterial infection - Staph. pseudintermedius
- dermatophyte infection
- Demodex mites
What is superficial pyoderma? What is it usually secondary to? What is the primary cause?
bacterial infection confined to the upper layers of the skin and hair follicle
allergies, anatomic predispositions (skin folds)
Staph. pseudintermedius - commensal bacteria on dog skin and mucosa
How does superficial pyoderma present? What is seen histologically?
papules, pustules, epidermal collarettes
pustular dermatitis and folliculitis with bacteria
What is intertrigo?
dermatitis occurring in areas of skin folding, such as face folds, lip folds, tail folds, and vulvar areas
- surface bacterial overgrowth (epidermal collarettes)
What is deep pyoderma? What breed is predisposed? What is the most common cause?
infection of the deep dermis and subcutis and deep portions of the follicle
German shepherds
Staph. pseudintermedius
How does deep pyoderma present? What is seen histologically?
erythema, ulcers, hemorrhagic crusts, bullae, draining tracts, and pain anywhere, but mostly on the truck and pressure points
folliculitis —> furunculosis and cellulitits
What causes post-grooming furunculosis? How does it present?
water immersion or exposure to grooming products contaminated with Pseudomonas aeruginosa
- acute deep pyoderma: hemorrhagic crusts, papules, pustules, draining tracts
- lethargy, fever, pain
What causes dermatophytosis in dogs, cats, horses, and ruminants? Is it zoonotic?
DOG: Microsporum canis
CAT: Microsporum gypseum
HORSE: Trichophyton equinum
RUMINANT: Trichophyton verrucosum
YES
What animals are predisposed to dermatophytosis?
- young animals
- Persians
- Himalayans
How does dermatophytosis present grossly? Histologically?
circular patches of scaling, alopecia, and papules (folliculitis)
folliculitis/furunculosis, arthrospores and hyphae in hair shafts
How is dermatophytosis diagnosed?
- hair pluck
- toothbrush technique and dermatophyte test medium
- PCR
Dermatophytosis, histology:
What typically causes Demodectic mange? How is it typically transmitted? What allows for disease to develop?
- Demodex canis
- Demodex injai (live deep in hair follicles —> deep skin scrape)
direct contact from mother to offspring during nursing (not much horizontal transfer)
underlying disease causing immunosuppression and folliculitis/furunculosis
How does Demodectic mange present?
alopecia, crusting, scaling, and variable pruritus on face, head, neck, truck, and limbs
Demodectic mange, histology:
folliculitis —> inflammatory cell invasion
Ulcerative/erosive dermatitis:
What causes feline herpesvirus dermatitis? How does it present? What can be accompanied by this infection?
Felid herpesvirus-1
erosions, ulcers, and crusts on the face/nasal planum and occasional limbs
- rhinitis
- conjunctivitis
What is seen histologically in feline herpesvirus dermatitis?
eosinophilic dermatitis with ulcers, necrosis, and intraepithelial intranuclear viral inclusion bodies
What causes contagious ecthyma? In what animals is it most common? How does it develop?
(orf, contagious pustular dermatitis, infectious labial dermatitis, soremouth, scabby mouth)
Parapoxvirus
sheep and goats
regression is usually complete by 4 weeks (zoonotic!)
How does contagious ecthyma (orf) present?
vesicles, pustules, ulcers, and crusts commonly on lips, muzzle, face, and oral cavity
What is seen histologically in contagious ecthyma (orf)?
epidermal hyperplasia, ballooning degeneration, eosinophilic intracytoplasmic inclusion bodies
What is irritant contact dermatitis? How is it different from allergic contact dermatitis?
nonspecific inflammatory cutaneous reaction caused by direct contact with an irritating agent, such as caustic chemicals, characterized by edema, erythema and papules developing into scales and lichenification
DOESN’T require prior sensitization
What causes thermal burns?
- strong chemicals
- electric currents
- solar/microwave radiation
- heating pads
- hair driers
- hot liquid
- lightning strike
What are the 3 types of photosensitization dermatitis?
TYPE I: primary —> ingestion of exogenous agents (plants with phytoporphorins, drugs)
TYPE II: endogenous —> congenital erythropoietic porphyria causing disturbance in porphyrin pigment metabolism
TYPE III: hepatogenous photosensitization —> plant toxins from Lantana camara and Senecio spp. and mycotoxins
What causes hepatogenous photosensitization? How does it present? In what areas of the body is it most common?
impaired capacity of the liver to excrete phytoporphyrins, which increases their levels in the blood, causing dermatitis
erythema progressing to crusting, erosion, and ulcers —> intensely pruritic
sun-exposed (face, ears) and lightly pigmented regions
