Transcript Non infectious dermatoses

Healing:
Prerequisites
for healing:
• First intention
• Debridement
• Second intention
• Tissue scaffold
• Germinal cells
• Blood supply
Reference reading: Repair of the skin pp318-322,
in Applied Veterinary Histology, W. J. Banks, 1993
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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)
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• Allergy (Hypersensitivity)
severe reaction to harmless foreign antigen
• Autoimmune dz
immune reaction against self-antigens
Pathogenesis:
tissue damage is mediated by four
immune reactions: Type I, II, III, and IV
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Immunologic diseases
IgE
Mast cell
Allergen
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Immunologic diseases
IgG
T cell
Cytotoxic effect
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Immunologic diseases
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Immunologic diseases
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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
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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)
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Immunologic diseases - Allergic dz
Diagnosis
• There is no single confirmatory test
• Skin biopsy
• Rule out other allergies
• Intradermal allergy testing
• ELISA for allergen specific IgE
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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
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Immunologic diseases - Allergic dz
Diagnosis
• Skin biopsy
• Demonstration of fleas
• Provocative exposure and response to therapy
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Immunologic diseases - Allergic dz
• Type I and/or type IV reactions
• Non-seasonal erythema, urticaria, alopecia, pruritus
with self-inflicted trauma (licking, rubbing)
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Immunologic diseases - Allergic dz
Diagnosis
• Skin biopsy
• Rule out other allergies
• Elimination diet trial (with absolute compliance)
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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
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Immunologic diseases
• Vesiculo-pustular dz often presented as
persistent erosions and crusting
• Autoimmune dz
immune reaction against self-antigens
• Mediated by type II or III reactions
• Variably pruritic, if not complicate by
pyoderma
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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)
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Immunologic diseases - Autoimmune dz
• Type III reaction
• Systemic lupus erythematosus
Multiorgan disease
• Discoid lupus erythematosus
Skin of the face
• Ab-Ag deposition
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Immunologic diseases - Autoimmune dz
• Autosomal dominant disease
• Puppies and young dogs
• Type III reaction - vasculitis
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Immunologic diseases - Autoimmune dz
• Clinical signs
• Histology
• Immunohistochemistry
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