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New page: {{toplink |backcolour = FFCCCC |linkpage =Integumentary System - Pathology |linktext =Integumentary System |maplink = Integumentary System (Content Map) - Pathology |pagetype =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 - Anatomy & Physiology|mast cells]] and [[Basophils - Anatomy & Physiology|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#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 - Anatomy & Physiology#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#Pemphigus|Pemphigus]]
**[[Skin - immunologic#Bullous pemphigoid|Bullous pemphigoid]]
===Type III reactions===
*[[Complement - Anatomy & Physiology#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 -> [[General Pathology - Haemorrhage#Purpura haemorrhagica|purpura haemorrhagica]]
*Includes:
**[[Skin - immunologic#Lupus erythematosus|Systemic lupus erythematosus]]
**[[Skin - immunologic#Dermatomyositis|Canine dermatomyositis]]
===Type IV reactions===
*Delayed hypersensitivity
*Haptens bind to carrier proteins (mainly epidermal)
*Mediated by sensitised [[General Pathology - T-cell Activation and Function|T-cells]] -> release cytokines +/- recruit lymphocytes
*Used in diagnosis of tuberculosis, histoplasmosis and coccidiomycosis
*Perivascular mononuclear cell accumulation
==Hypersensitivity reactions==
===Atopy===
*Involves [[Skin - immunologic#Type I reactions|Type I reaction]]
*Mainly causes pruritus
*Dogs - face rubbing and foot licking; secondary [[Bacterial skin infections - Pathology#Pyoderma|pyoderma]] or seborrhea
*Cats - facial, ear or generalised pruritus, miliary dermatitis, [[Skin - other#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
===Flea bite hypersensitivity===
*Usually involves [[Skin - immunologic#Type I reactions|Type I reaction]] and [[Skin - immunologic#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:
**Papular dermatitis
**Secondary excoriations
**Alopecic nodule if chronic
*Microscopically:
**Hyperplastic superficial perivascular dermatitis
**Oedema, [[Mast cells - Anatomy & Physiology|mast cells]], [[Basophils - Anatomy & Physiology|basophils]], [[Eosinophils - Anatomy & Physiology|eosinophils]], [[Lymphocytes - Anatomy & Physiology|lymphocytes]], histiocytes
**Fibropruritic nodules covered by hyperplastic epidermis
===Culicoides hypersensitivity===
*Usually involves [[Skin - immunologic#Type I reactions|Type I reaction]] and [[Skin - immunologic#Type IV reactions|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 [[Skin - other#Eosinophilic granuloma|eosinophilic granulomas]]
===Allergic contact dermatitis===
*Usually involves [[Skin - immunologic#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 - Anatomy & Physiology|eosinophils]]
==Autoimmune reactions==
BS-to-finish
===Dermatomyositis===
*See also [[Muscles - developmental#Canine dermatomyositis|Canine dermatomyositis]]
|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 - Anatomy & Physiology|mast cells]] and [[Basophils - Anatomy & Physiology|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#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 - Anatomy & Physiology#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#Pemphigus|Pemphigus]]
**[[Skin - immunologic#Bullous pemphigoid|Bullous pemphigoid]]
===Type III reactions===
*[[Complement - Anatomy & Physiology#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 -> [[General Pathology - Haemorrhage#Purpura haemorrhagica|purpura haemorrhagica]]
*Includes:
**[[Skin - immunologic#Lupus erythematosus|Systemic lupus erythematosus]]
**[[Skin - immunologic#Dermatomyositis|Canine dermatomyositis]]
===Type IV reactions===
*Delayed hypersensitivity
*Haptens bind to carrier proteins (mainly epidermal)
*Mediated by sensitised [[General Pathology - T-cell Activation and Function|T-cells]] -> release cytokines +/- recruit lymphocytes
*Used in diagnosis of tuberculosis, histoplasmosis and coccidiomycosis
*Perivascular mononuclear cell accumulation
==Hypersensitivity reactions==
===Atopy===
*Involves [[Skin - immunologic#Type I reactions|Type I reaction]]
*Mainly causes pruritus
*Dogs - face rubbing and foot licking; secondary [[Bacterial skin infections - Pathology#Pyoderma|pyoderma]] or seborrhea
*Cats - facial, ear or generalised pruritus, miliary dermatitis, [[Skin - other#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
===Flea bite hypersensitivity===
*Usually involves [[Skin - immunologic#Type I reactions|Type I reaction]] and [[Skin - immunologic#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:
**Papular dermatitis
**Secondary excoriations
**Alopecic nodule if chronic
*Microscopically:
**Hyperplastic superficial perivascular dermatitis
**Oedema, [[Mast cells - Anatomy & Physiology|mast cells]], [[Basophils - Anatomy & Physiology|basophils]], [[Eosinophils - Anatomy & Physiology|eosinophils]], [[Lymphocytes - Anatomy & Physiology|lymphocytes]], histiocytes
**Fibropruritic nodules covered by hyperplastic epidermis
===Culicoides hypersensitivity===
*Usually involves [[Skin - immunologic#Type I reactions|Type I reaction]] and [[Skin - immunologic#Type IV reactions|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 [[Skin - other#Eosinophilic granuloma|eosinophilic granulomas]]
===Allergic contact dermatitis===
*Usually involves [[Skin - immunologic#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 - Anatomy & Physiology|eosinophils]]
==Autoimmune reactions==
BS-to-finish
===Dermatomyositis===
*See also [[Muscles - developmental#Canine dermatomyositis|Canine dermatomyositis]]