E. Simko WCVM

Healing:• First intention

• Second intention

Prerequisites for healing:• Debridement

• Tissue scaffold

• Germinal cells

• Blood supply

Reference reading: Repair of the skin pp318-322, in Applied Veterinary Histology, W. J. Banks, 1993

• Extreme temperatures (cold and burns)• Solar injury (direct effect and photosensitization)

• Chemical/toxic injuries (ergot, fescue, Se) • Self-inflicted injury

Acral lick dermatitis (lick granuloma)

Feline psychogenic alopecia

Pyotraumatic dermatitis (hot spots)

• Injection site reactions• Intertrigo (skin fold dermatitis)

E. Simko WCVM

• Allergy (Hypersensitivity)severe reaction to harmless foreign antigen

E. Simko WCVM

• Autoimmune dzimmune reaction against self-antigens

Pathogenesis:tissue damage is mediated by four immune reactions: Type I, II, III, and IV

Immunologic diseases

Allergen

IgE

Mast cell

E. Simko WCVM

Immunologic diseases

E. Simko WCVM

IgG

Cytotoxic effect

Complement

T cell

Immunologic diseases

E. Simko WCVM

ComplementImmune complex deposition

Immunologic diseases

SensitizedT cell

Antigens

Cytokines Chemotaxis and activation of

macrophages

E. Simko WCVM

Immunologic diseases

• Allergy (Hypersensitivity)severe reaction to harmless foreign

antigen

• Mediated by type I and/or type IV reactions

• Common in dogs and horses, less common in cats and uncommon in food animals

• Erythema, pruritus, self-induced trauma E. Simko WCVM

Immunologic diseases - Allergic dz

• Inherited predisposition to type I reaction

• Average age of onset is from 1 to 3 years

• Respiratory route of allergen exposure (dogs)

• Lesions: erythema, urticaria,

self-inflicted trauma (licking, rubbing)

E. Simko WCVM

Immunologic diseases - Allergic dz

• There is no single confirmatory test

• Skin biopsy

• Rule out other allergies

• Intradermal allergy testing

• ELISA for allergen specific IgE

Diagnosis

E. Simko WCVM

Immunologic diseases - Allergic dz

• Most common allergic dermatitis in dogs and cats

• Type I and type IV reactions to flea saliva

• Seasonal pruritus with self-inflicted trauma(excoriation) and alopecia

E. Simko WCVM

Immunologic diseases - Allergic dz

• Skin biopsy

• Demonstration of fleas

• Provocative exposure and response to therapy

Diagnosis

E. Simko WCVM

Immunologic diseases - Allergic dz

• Type I and/or type IV reactions

• Non-seasonal erythema, urticaria, alopecia, pruritus

with self-inflicted trauma (licking, rubbing)

E. Simko WCVM

Immunologic diseases - Allergic dz

• Skin biopsy

• Rule out other allergies

• Elimination diet trial (with absolute compliance)

Diagnosis

E. Simko WCVM

Immunologic diseases - Allergic dz

• Type IV reaction to chemicals (dyes, plant, soaps, detergents,…)

• Erythema, pruritus with self-inflicted trauma (exudation, crusts, alopecia)

• Diagnosis

Skin biopsy

Elimination trial

E. Simko WCVM

Immunologic diseases

• Vesiculo-pustular dz often presented as persistent erosions and crusting

• Autoimmune dzimmune reaction against self-antigens

• Mediated by type II or III reactions

• Variably pruritic, if not complicate by

pyodermaE. Simko WCVM

Immunologic diseases - Autoimmune dz

• Group of vesicular/pustular diseases

• Pemphigus foliaceus (Ca, Fe, Eq, Cap) Acantholysis (anti-desmosomal antibodies)

• Bullous pemphigoid (Ca, Eq)(anti-hemidesmosomal antibodies)

E. Simko WCVM

Immunologic diseases - Autoimmune dz

• Type III reaction

• Systemic lupus erythematosus

Multiorgan disease

• Discoid lupus erythematosus

Skin of the face

• Ab-Ag deposition

E. Simko WCVM

Immunologic diseases - Autoimmune dz

• Autosomal dominant disease

• Puppies and young dogs

• Type III reaction - vasculitis

E. Simko WCVM

Immunologic diseases - Autoimmune dz

• Clinical signs

• Histology

• Immunohistochemistry

E. Simko WCVM