| Line 1: |
Line 1: |
| − | {{review}}
| + | #REDIRECT[[:Category:Integumentary System - Immunologic Pathology]] |
| − | | |
| − | {{toplink
| |
| − | |backcolour = FFCCCC
| |
| − | |linkpage =Integumentary System - Pathology
| |
| − | |linktext =Integumentary System
| |
| − | |maplink = Integumentary System (Content Map) - Pathology
| |
| − | |pagetype =Pathology
| |
| − | }}
| |
| − | <br>
| |
| − | | |
| − | ==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|mast cells]] and [[Basophils|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:
| |
| − | **[[Skin Immunologic - Pathology#Atopy|Atopic dermatitis]]
| |
| − | **[[Skin Glossary - Pathology|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#Complement Fixation Pathways|complement fixation]] -> cellular damage
| |
| − | *In skin - circulating antibody to proteins of desmosomes in intercellular areas along basement membranes at epidermal-dermal junction
| |
| − | *Includes:
| |
| − | **[[Skin Immunologic - Pathology#Pemphigus|Pemphigus]]
| |
| − | **[[Skin Immunologic - Pathology#Bullous pemphigoid|Bullous pemphigoid]]
| |
| − | | |
| − | ===Type III reactions===
| |
| − | *[[Complement#Complement Fixation Pathways|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 -> [[Haemorrhage#Purpura haemorrhagica|purpura haemorrhagica]]
| |
| − | *Includes:
| |
| − | **[[Skin Immunologic - Pathology#Lupus erythematosus|Systemic lupus erythematosus]]
| |
| − | **[[Skin Immunologic - Pathology#Dermatomyositis|Canine dermatomyositis]]
| |
| − | | |
| − | ===Type IV reactions===
| |
| − | *Delayed hypersensitivity
| |
| − | *Haptens bind to carrier proteins (mainly epidermal)
| |
| − | *Mediated by sensitised [[T cell differentiation|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 [[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|eosinophils]]
| |
| − | | |
| − | ===Atopy===
| |
| − | | |
| − | *Involves [[Skin Immunologic - Pathology#Type I reactions|Type I reaction]]
| |
| − | *Mainly causes pruritus
| |
| − | *Dogs - face rubbing and foot licking; secondary [[Bacterial skin infections - Pathology#Pyoderma|pyoderma]] or [[Skin Other - Pathology#Secondary seborrhea|seborrhea]]
| |
| − | *Cats - facial, ear or generalised pruritus, miliary dermatitis, [[Skin Other - Pathology#Eosinophilic granuloma|eosinophilic granuloma complex]], symmetric alopecia
| |
| − | *Horses - pruritic hea, pinnae, ventrum, legs, tailhead or recurrent [[Skin Glossary - Pathology|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]]===
| |
| − | | |
| − | ===[[Flea Bite Hypersensitivity]]===
| |
| − | | |
| − | | |
| − | | |
| − | ==Autoimmune reactions==
| |
| − | | |
| − | ===Bullous pemphigoid===
| |
| − | | |
| − | *Dogs and horses
| |
| − | *Involves oral cavity, mucocutaneous junctions, groin and axilla
| |
| − | *Subepidermal vesicles and bullae
| |
| − | *Antibodies bound to basement membrane
| |
| − | *Grossly:
| |
| − | **Similar to [[Skin Immunologic - Pathology#Pemphigus|Pemphigus vulgaris]]
| |
| − | *Microscopically:
| |
| − | **Bullae containing fibrin, [[Neutrophils|neutrophils]] or [[Eosinophils|eosinophils]]
| |
| − | **Basement membrane forms floor of bullae and roof is lined with basal cells
| |
| − | *Bullae may rupture -> ulcers
| |
| − | | |
| − | ===Dermatomyositis===
| |
| − | *See also [[Muscles Developmental - Pathology#Canine dermatomyositis|Canine dermatomyositis]]
| |
| − | *Affects puppies of collies and shetland sheepdogs from 8 weeks of age
| |
| − | *Lesions - vesiculating dermatitis
| |
| − | **Face, lips, external ears, later distal extremities
| |
| − | *Microscopically: interface dermatitis and basal cell degeneration of epidermis and follicular wall, atrophy of follicles, epidermal vesicles and pustules, dermal scarring
| |
| − | | |
| − | ===Lupus erythematosus===
| |
| − | | |
| − | *'''Systemic (SLE)'''
| |
| − | **Multiple organs involved
| |
| − | **Cats, dogs, horses
| |
| − | **Immune dysregulation:
| |
| − | ***Damaged T-cell suppressor function, either primary deficiency or antibody mediated
| |
| − | ***Cytokine dysregulation
| |
| − | ***Resulting B-cell hyperactivity -> antibodies to self antigens -> antigen-antibody complexes deposited in various tissues -> Type III hypersensitivity
| |
| − | **Lesions localised or generalised
| |
| − | **Erythema, alopecia, depigmentation, crusting and scaling, ulceration
| |
| − | **Microscopically: lymphohistiocytic interface dermatitis, thickened basement membrane, vasculitis, subepidermal vesicles, basal cell degeneration
| |
| − | *'''Discoid'''
| |
| − | **Milder variant of systemic
| |
| − | **Depigmentation, erythema, scaling, erosions, ulceration, crusting
| |
| − | **Usually involves nasal planum, dorsum of muzzle, occasionally pinnae, lips, oral mucosa or periocular area
| |
| − | **Microscopically: lichenoid interface dermatitis, often with lymphocytes, plasma cells, basal cell degeneration, loss of pigment
| |
| − | | |
| − | ===[[Pemphigus]]===
| |