Difference between revisions of "Skin Immunologic - Pathology"

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#REDIRECT[[:Category:Integumentary System - Immunologic Pathology]]
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{{review}}
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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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<br>
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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 - WikiBlood|mast cells]] and [[Basophils - WikiBlood|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 -> [[General Pathology - 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 - 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 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 - WikiBlood|basophils]], [[Eosinophils - WikiBlood|eosinophils]], [[Lymphocytes - WikiBlood|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 - WikiBlood|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===
 +
 
 +
*Blistering diseases
 +
*Autoantibodies bind to desmosomal proteins -> cell adhesion disrupted -> vesicles
 +
*Types:
 +
**'''Pemphigus vulgaris'''
 +
***Rare, severe form
 +
***Cats and dogs
 +
***Vesicles or bullae -> erosions and ulcers
 +
***Involves oral cavity, mucocutaneous junctions and skin
 +
***Microscopically:
 +
****Suprabasilar vesiculation and row of basal cells adhering to basement membrane
 +
****Superficial perivascular dermatitis
 +
**'''Pemphigus vegetans'''
 +
***Rare
 +
***Dogs
 +
***Involves the trunk
 +
***Mild version of P. vulgaris
 +
***Vesicopustular dermatitis + epidermal hyperplasia -> papillomatous formations
 +
**'''Pemphigus foliaceus'''
 +
***More common
 +
***Cats, dogs, horses, goats
 +
***Localised lesions or generalised
 +
***Symmetrical vesicular or pustular dermatitis, crusts, scales, alopecia
 +
***Microscopically:
 +
****Acantholytic cells
 +
****Subcorneal or intragranular pustules
 +
****In third of equine or canine cases [[Eosinophils - WikiBlood|eosinophils]] are predominant
 +
**'''Pemphigus erythematosus'''
 +
***Cats and dogs
 +
***Mild form of P. foliaceus
 +
***Usually involves only face and external ears

Revision as of 11:28, 30 October 2008

 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.


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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:
  • 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

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:

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:
  • 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

Pemphigus

  • Blistering diseases
  • Autoantibodies bind to desmosomal proteins -> cell adhesion disrupted -> vesicles
  • Types:
    • Pemphigus vulgaris
      • Rare, severe form
      • Cats and dogs
      • Vesicles or bullae -> erosions and ulcers
      • Involves oral cavity, mucocutaneous junctions and skin
      • Microscopically:
        • Suprabasilar vesiculation and row of basal cells adhering to basement membrane
        • Superficial perivascular dermatitis
    • Pemphigus vegetans
      • Rare
      • Dogs
      • Involves the trunk
      • Mild version of P. vulgaris
      • Vesicopustular dermatitis + epidermal hyperplasia -> papillomatous formations
    • Pemphigus foliaceus
      • More common
      • Cats, dogs, horses, goats
      • Localised lesions or generalised
      • Symmetrical vesicular or pustular dermatitis, crusts, scales, alopecia
      • Microscopically:
        • Acantholytic cells
        • Subcorneal or intragranular pustules
        • In third of equine or canine cases eosinophils are predominant
    • Pemphigus erythematosus
      • Cats and dogs
      • Mild form of P. foliaceus
      • Usually involves only face and external ears
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