Difference between revisions of "Skin Immunologic - Pathology"
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==Hypersensitivity reactions== | ==Hypersensitivity reactions== | ||
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+ | ===Allergic contact dermatitis=== | ||
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+ | *Usually involves [[Skin Immunologic - Pathology#Type IV reactions|Type IV reaction]] | ||
+ | *Pruritic lesions with self-inflicted trauma | ||
+ | *At areas in contact with allergen | ||
+ | *Grossly: | ||
+ | **Erythema, papules, +/- vesicles, exudation -> crusts | ||
+ | **If chronic, lichenification, hyperpigmentation, alopecia | ||
+ | *Microscopically: | ||
+ | **Spongiotic superficial perivascular dermatitis | ||
+ | **Mononuclear cells | ||
+ | **If chronic, epidermal hyperplasia | ||
+ | **May involve [[Eosinophils - WikiBlood|eosinophils]] | ||
===Atopy=== | ===Atopy=== | ||
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**Mast cells, eosinophils, nonmetachromatic mononuclear cells | **Mast cells, eosinophils, nonmetachromatic mononuclear cells | ||
**Perivascular inflammation may be involved especially in horses | **Perivascular inflammation may be involved especially in horses | ||
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===Culicoides hypersensitivity=== | ===Culicoides hypersensitivity=== | ||
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**Possibly eosinophilic folliculitis, intraepidermal pustules and [[Skin Other - Pathology#Eosinophilic granuloma|eosinophilic granulomas]] | **Possibly eosinophilic folliculitis, intraepidermal pustules and [[Skin Other - Pathology#Eosinophilic granuloma|eosinophilic granulomas]] | ||
− | === | + | ===Flea bite hypersensitivity=== |
− | *Usually involves [[Skin Immunologic - Pathology#Type IV reactions|Type IV reaction]] | + | *Usually involves [[Skin Immunologic - Pathology#Type I reactions|Type I reaction]] and [[Skin Immunologic - Pathology#Type IV reactions|Type IV reaction]] and cutaneous basophil hypersensitivity |
− | * | + | *Mainly dorsolumbosacral area involved, abdomen, caudomedial thighs, flanks, neck of cats |
− | + | *Secondary trauma is self-inflicted | |
*Grossly: | *Grossly: | ||
− | ** | + | **Papular dermatitis |
− | ** | + | **Secondary excoriations |
+ | **Alopecic nodule if chronic | ||
*Microscopically: | *Microscopically: | ||
− | ** | + | **Hyperplastic superficial perivascular dermatitis |
− | ** | + | **Oedema, [[Mast Cells - WikiBlood|mast cells]], [[Basophils - WikiBlood|basophils]], [[Eosinophils - WikiBlood|eosinophils]], [[Lymphocytes - WikiBlood|lymphocytes]], histiocytes |
− | + | **Fibropruritic nodules covered by hyperplastic epidermis | |
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==Autoimmune reactions== | ==Autoimmune reactions== |
Revision as of 10:32, 11 October 2008
This article is still under construction. |
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General
- Classification:
- Hypersensitivity - response to normally harmless substances
- Auto-immune - antobodies or T-cells reactive against self-antigens
- Mostly involves mixture of types described below
Type I reactions
- Mediated by pharmacologically active substances from mast cells and basophils
- Due to antigen-antibody (usually IgE) binding to receptors on those cells
- Substances include histamine, serotonin, leukotriens, prostaglandins
- Can be systemic or local
- Skin becomes pruritic, raised erythematous borders of wheals
- Immediate reaction
- Includes:
- Atopic dermatitis
- Urticaria
- Angioedema
- Fly bite hypersensitivity
- Gastrointestinal parasites
- Food
- Microscopically:
- Capillary dilation, oedema, mast cell degranulation, eosinophil infiltration
Type II reactions
- Cytotoxic reaction
- IgG and IgM interaction with antigens bound to cellular membranes
- Often involves complement fixation -> cellular damage
- In skin - circulating antibody to proteins of desmosomes in intercellular areas along basement membranes at epidermal-dermal junction
- Includes:
Type III reactions
- Complement fixing immune complexes
- IgG or IgM
- Complexes deposit in tissue -> fix complement -> cytokines and othe factors attrack neutrophils -> release lysosomal enzymes, activation of complement and coagulation, platelet aggregation -> tissue damage
- Immune complex vasculitis -> purpura haemorrhagica
- Includes:
Type IV reactions
- Delayed hypersensitivity
- Haptens bind to carrier proteins (mainly epidermal)
- Mediated by sensitised T-cells -> release cytokines +/- recruit lymphocytes
- Used in diagnosis of tuberculosis, histoplasmosis and coccidiomycosis
- Perivascular mononuclear cell accumulation
Hypersensitivity reactions
Allergic contact dermatitis
- Usually involves Type IV reaction
- Pruritic lesions with self-inflicted trauma
- At areas in contact with allergen
- Grossly:
- Erythema, papules, +/- vesicles, exudation -> crusts
- If chronic, lichenification, hyperpigmentation, alopecia
- Microscopically:
- Spongiotic superficial perivascular dermatitis
- Mononuclear cells
- If chronic, epidermal hyperplasia
- May involve eosinophils
Atopy
- Involves Type I reaction
- Mainly causes pruritus
- Dogs - face rubbing and foot licking; secondary pyoderma or seborrhea
- Cats - facial, ear or generalised pruritus, miliary dermatitis, eosinophilic granuloma complex, symmetric alopecia
- Horses - pruritic hea, pinnae, ventrum, legs, tailhead or recurrent urticaria
- Lesions generally due to self-trauma
- Microscopically:
- Hyperplastic superficial perivascular dermatitis
- Mast cells, eosinophils, nonmetachromatic mononuclear cells
- Perivascular inflammation may be involved especially in horses
Culicoides hypersensitivity
- Usually involves Type I reaction and Type IV reaction due to salivary antigens of Culicoides sp.
- May be seasonally recurring or continuous depending on climate
- Grossly:
- Papules, crusts, alopecia, excoriations, lichenification
- Microscopically:
- Superficial and dep perivascular dermatitis
- Many eosinophils
- Epidermal hyperplasia
- Hyperkeratosis
- Dermal fibrosis
- Possibly eosinophilic folliculitis, intraepidermal pustules and eosinophilic granulomas
Flea bite hypersensitivity
- Usually involves Type I reaction and Type IV reaction and cutaneous basophil hypersensitivity
- Mainly dorsolumbosacral area involved, abdomen, caudomedial thighs, flanks, neck of cats
- Secondary trauma is self-inflicted
- Grossly:
- Papular dermatitis
- Secondary excoriations
- Alopecic nodule if chronic
- Microscopically:
- Hyperplastic superficial perivascular dermatitis
- Oedema, mast cells, basophils, eosinophils, lymphocytes, histiocytes
- Fibropruritic nodules covered by hyperplastic epidermis
Autoimmune reactions
BS-to-finish
Dermatomyositis
- See also Canine dermatomyositis