Difference between revisions of "Skin Immunologic - Pathology"
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− | # | + | {{review}} |
+ | |||
+ | {{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 - WikiBlood|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 - WikiBlood#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 - WikiBlood#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 - Pathology#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 - WikiBlood|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 - WikiBlood|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=== | ||
+ | |||
+ | *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. | ||
+ | *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 - Pathology#Eosinophilic granuloma|eosinophilic granulomas]] | ||
+ | |||
+ | ===Flea bite hypersensitivity=== | ||
+ | |||
+ | *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: | ||
+ | **Papular dermatitis | ||
+ | **Secondary excoriations | ||
+ | **Alopecic nodule if chronic | ||
+ | *Microscopically: | ||
+ | **Hyperplastic superficial perivascular dermatitis | ||
+ | **Oedema, [[Mast Cells - WikiBlood|mast cells]], [[Basophils|basophils]], [[Eosinophils - WikiBlood|eosinophils]], [[Lymphocytes|lymphocytes]], histiocytes | ||
+ | **Fibropruritic nodules covered by hyperplastic epidermis | ||
+ | |||
+ | ==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 - WikiBlood|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]]=== |
Revision as of 12:45, 12 June 2010
This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing. |
|
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
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 Pemphigus vulgaris
- Microscopically:
- Bullae containing fibrin, neutrophils or eosinophils
- Basement membrane forms floor of bullae and roof is lined with basal cells
- Bullae may rupture -> ulcers
Dermatomyositis
- See also 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