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| − | {{review}}
| + | #REDIRECT[[:Category:Integumentary System - Immunologic Pathology]] |
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| − | {{toplink
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| − | |backcolour = FFCCCC
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| − | |linkpage =Integumentary System - Pathology
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| − | |linktext =Integumentary System
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| − | |maplink = Integumentary System (Content Map) - Pathology
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| − | |pagetype =Pathology
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| − | }}
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| − | <br>
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| − | ==General==
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| − | *Classification:
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| − | **Hypersensitivity - response to normally harmless substances
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| − | **Auto-immune - antobodies or T-cells reactive against self-antigens
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| − | *Mostly involves mixture of types described below
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| − | ===Type I reactions===
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| − | *Mediated by pharmacologically active substances from [[Mast Cells|mast cells]] and [[Basophils|basophils]]
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| − | **Due to antigen-antibody (usually [[IgE]]) binding to receptors on those cells
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| − | *Substances include histamine, serotonin, leukotriens, prostaglandins
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| − | *Can be systemic or local
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| − | *Skin becomes pruritic, raised erythematous borders of wheals
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| − | *Immediate reaction
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| − | *Includes:
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| − | **[[Skin Immunologic - Pathology#Atopy|Atopic dermatitis]]
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| − | **[[Skin Glossary - Pathology|Urticaria]]
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| − | **Angioedema
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| − | **Fly bite hypersensitivity
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| − | **Gastrointestinal parasites
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| − | **Food
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| − | *Microscopically:
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| − | **Capillary dilation, oedema, mast cell degranulation, eosinophil infiltration
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| − | ===Type II reactions===
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| − | *Cytotoxic reaction
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| − | *[[IgG]] and [[IgM]] interaction with antigens bound to cellular membranes
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| − | *Often involves [[Complement#Complement Fixation Pathways|complement fixation]] -> cellular damage
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| − | *In skin - circulating antibody to proteins of desmosomes in intercellular areas along basement membranes at epidermal-dermal junction
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| − | *Includes:
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| − | **[[Skin Immunologic - Pathology#Pemphigus|Pemphigus]]
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| − | **[[Skin Immunologic - Pathology#Bullous pemphigoid|Bullous pemphigoid]]
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| − | ===Type III reactions===
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| − | *[[Complement#Complement Fixation Pathways|Complement fixing]] immune complexes
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| − | *[[IgG]] or [[IgM]]
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| − | *Complexes deposit in tissue -> fix complement -> cytokines and othe factors attrack neutrophils -> release lysosomal enzymes, activation of complement and coagulation, platelet aggregation -> tissue damage
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| − | *Immune complex vasculitis -> [[Haemorrhage - Pathology#Purpura haemorrhagica|purpura haemorrhagica]]
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| − | *Includes:
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| − | **[[Skin Immunologic - Pathology#Lupus erythematosus|Systemic lupus erythematosus]]
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| − | **[[Skin Immunologic - Pathology#Dermatomyositis|Canine dermatomyositis]]
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| − | | |
| − | ===Type IV reactions===
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| − | *Delayed hypersensitivity
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| − | *Haptens bind to carrier proteins (mainly epidermal)
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| − | *Mediated by sensitised [[T cell differentiation - WikiBlood|T-cells]] -> release cytokines +/- recruit lymphocytes
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| − | *Used in diagnosis of tuberculosis, histoplasmosis and coccidiomycosis
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| − | *Perivascular mononuclear cell accumulation
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| − | ==Hypersensitivity reactions==
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| − | ===Allergic contact dermatitis===
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| − | *Usually involves [[Skin Immunologic - Pathology#Type IV reactions|Type IV reaction]]
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| − | *Pruritic lesions with self-inflicted trauma
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| − | *At areas in contact with allergen
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| − | *Grossly:
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| − | **Erythema, papules, +/- vesicles, exudation -> crusts
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| − | **If chronic, lichenification, hyperpigmentation, alopecia
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| − | *Microscopically:
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| − | **Spongiotic superficial perivascular dermatitis
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| − | **Mononuclear cells
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| − | **If chronic, epidermal hyperplasia
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| − | **May involve [[Eosinophils|eosinophils]]
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| − | ===Atopy===
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| − | *Involves [[Skin Immunologic - Pathology#Type I reactions|Type I reaction]]
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| − | *Mainly causes pruritus
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| − | *Dogs - face rubbing and foot licking; secondary [[Bacterial skin infections - Pathology#Pyoderma|pyoderma]] or [[Skin Other - Pathology#Secondary seborrhea|seborrhea]]
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| − | *Cats - facial, ear or generalised pruritus, miliary dermatitis, [[Skin Other - Pathology#Eosinophilic granuloma|eosinophilic granuloma complex]], symmetric alopecia
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| − | *Horses - pruritic hea, pinnae, ventrum, legs, tailhead or recurrent [[Skin Glossary - Pathology|urticaria]]
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| − | *Lesions generally due to self-trauma
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| − | *Microscopically:
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| − | **Hyperplastic superficial perivascular dermatitis
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| − | **Mast cells, eosinophils, nonmetachromatic mononuclear cells
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| − | **Perivascular inflammation may be involved especially in horses
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| − | ===Culicoides hypersensitivity===
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| − | *Usually involves [[Skin Immunologic - Pathology#Type I reactions|Type I reaction]] and [[Skin Immunologic - Pathology#Type IV reactions|Type IV reaction]] due to salivary antigens of ''Culicoides'' sp.
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| − | *May be seasonally recurring or continuous depending on climate
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| − | *Grossly:
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| − | **Papules, crusts, alopecia, excoriations, lichenification
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| − | *Microscopically:
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| − | **Superficial and dep perivascular dermatitis
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| − | **Many eosinophils
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| − | **Epidermal hyperplasia
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| − | **Hyperkeratosis
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| − | **Dermal fibrosis
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| − | **Possibly eosinophilic folliculitis, intraepidermal pustules and [[Skin Other - Pathology#Eosinophilic granuloma|eosinophilic granulomas]]
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| − | ===Flea bite hypersensitivity===
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| − | *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
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| − | *Mainly dorsolumbosacral area involved, abdomen, caudomedial thighs, flanks, neck of cats
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| − | *Secondary trauma is self-inflicted
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| − | *Grossly:
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| − | **Papular dermatitis
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| − | **Secondary excoriations
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| − | **Alopecic nodule if chronic
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| − | *Microscopically:
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| − | **Hyperplastic superficial perivascular dermatitis
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| − | **Oedema, [[Mast Cells|mast cells]], [[Basophils|basophils]], [[Eosinophils|eosinophils]], [[Lymphocytes|lymphocytes]], histiocytes
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| − | **Fibropruritic nodules covered by hyperplastic epidermis
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| − | ==Autoimmune reactions==
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| − | ===Bullous pemphigoid===
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| − | *Dogs and horses
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| − | *Involves oral cavity, mucocutaneous junctions, groin and axilla
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| − | *Subepidermal vesicles and bullae
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| − | *Antibodies bound to basement membrane
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| − | *Grossly:
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| − | **Similar to [[Skin Immunologic - Pathology#Pemphigus|Pemphigus vulgaris]]
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| − | *Microscopically:
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| − | **Bullae containing fibrin, [[Neutrophils|neutrophils]] or [[Eosinophils|eosinophils]]
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| − | **Basement membrane forms floor of bullae and roof is lined with basal cells
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| − | *Bullae may rupture -> ulcers
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| − | ===Dermatomyositis===
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| − | *See also [[Muscles Developmental - Pathology#Canine dermatomyositis|Canine dermatomyositis]]
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| − | *Affects puppies of collies and shetland sheepdogs from 8 weeks of age
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| − | *Lesions - vesiculating dermatitis
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| − | **Face, lips, external ears, later distal extremities
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| − | *Microscopically: interface dermatitis and basal cell degeneration of epidermis and follicular wall, atrophy of follicles, epidermal vesicles and pustules, dermal scarring
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| − | ===Lupus erythematosus===
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| − | *'''Systemic (SLE)'''
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| − | **Multiple organs involved
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| − | **Cats, dogs, horses
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| − | **Immune dysregulation:
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| − | ***Damaged T-cell suppressor function, either primary deficiency or antibody mediated
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| − | ***Cytokine dysregulation
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| − | ***Resulting B-cell hyperactivity -> antibodies to self antigens -> antigen-antibody complexes deposited in various tissues -> Type III hypersensitivity
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| − | **Lesions localised or generalised
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| − | **Erythema, alopecia, depigmentation, crusting and scaling, ulceration
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| − | **Microscopically: lymphohistiocytic interface dermatitis, thickened basement membrane, vasculitis, subepidermal vesicles, basal cell degeneration
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| − | *'''Discoid'''
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| − | **Milder variant of systemic
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| − | **Depigmentation, erythema, scaling, erosions, ulceration, crusting
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| − | **Usually involves nasal planum, dorsum of muzzle, occasionally pinnae, lips, oral mucosa or periocular area
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| − | **Microscopically: lichenoid interface dermatitis, often with lymphocytes, plasma cells, basal cell degeneration, loss of pigment
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| − | ===[[Pemphigus]]===
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