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Skin Environmental - Pathology (view source)
Revision as of 12:01, 31 July 2008
, 12:01, 31 July 2008New 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>
==Chemical damage==
===Contact dermatitis===
*Results due to exposure to chemicals (not immunologic reaction)
**Acids, alkali, detergents, irritant plants ''etc.''
*In cats and dogs lesions usually on skin of abdomen, feet, chest, eyelids, axillae
*In horses lesions on muzzle, lower limbs, under tack
*Grossly:
**Erythematous [[Skin Glossary - Pathology|pathes and papules]]
**Occasionally [[Skin Glossary - Pathology|vesicles]]
**Lesions caused by self-trauma include [[Skin Glossary - Pathology|ulcers and crusts]]
*Microscopically:
**Hyperplastic, spongiotic dermatitis
**Superficial perivascular inflammation
**Necrosis may be caused by corrosive substances
===Ergot poisoning===
*Caused by ingestion of grains or grass contaminated by fungus ''Claviceps purpurae''
*Affects especially cattle
*Toxic alkaloids damage capillary endothelium, peripheral arterial and venous constriction -> thrombosis and possible tissue ischaemia
*Clinical signs develop about a week after consumption
*Grossly:
**Red and swollen extremities
**[[General Pathology - Necrosis#Dry Gangrene|Dry gangrene]] may develop on pinnae and tail
===Fescue poisoning===
*Caused by excessive consumption of ''Festuca arudinacea''
*Clinical signs develop about two weeks after consumption
*Grossly:
**[[General Pathology - Necrosis#Dry Gangrene|Dry gangrene]] of extremities
**Similar to [[Skin - environmental#Ergot poisoning|ergot poisoning]]
===Selenium poisoning===
*Caused by ingestion of plants that have accummulated excessive amounts of selenium
*May affect any herbivore, possibly also pigs
*Acute poisoning:
**Multiple organ systems are involved
*Chronic poisoning
**Poor hair quality, partial alopecia
**Horses - loss of main and tail hair, deformed hooves that may be shed
==Physical damage==
===Acral lick dermatitis===
*Also called '''lick granuloma''' or '''neurodermatitis'''
*Mostly occurs in dogs due to constant licking or chewing
*Areas most affected are carpal, metacarpal, metatarsal, radial or tibial areas
*Usually a single lesion
*Grossly:
**Circumscribed hairless areas that may ulcerate
*Microscopically:
**Compact [[Skin Glossary - Pathology|hyperkeratosis]]
**Hyperplasia of follicular and epidermal epithelium and sebaceous glands
**Collagenous fibres causing dermal thickening
**Perivascular and periadnexal plasma cell accumulation
**May be associated with mild snsory polyneuropathy
===Feline psychogenic alopecia===
*Occurs in cats
*Broken hairs cused by persistent licking -> partial alopecia
*Areas mostly affected: dorsal midline, perineal, genital, medial thigh, abdomen
*Microscopically:
**Usually normal skin
**Possibly increased [[Skin Glossary - Pathology|telogen]] follicles
===Callus===
*Hypertrophy of epidermis, particularly at pressure points
*Usually affects giant breed dogs and pigs kept on hard floor
*May be followed by folliculitis, [[Skin Glossary - Pathology|furunculosis]] and ulceration
*Microscopically:
**[[Skin Glossary - Pathology|Hyperkeratosis and acanthosis]] or epidermis and follicular epithelium
**[[Skin Glossary - Pathology|Comedones]] and follicular cysts may be present, potentially rupture and cause secondary pyoderma
**Excessive keratin widening follicular openings
===Injection site reaction===
*May be caused by subcutaneous injections
*Granulomatous nodules form with central necrotic and foreign material
*Macrophages and multinucleated giant cells around the centre
*Surrounded by granulation tissue, perivascular lymphocytes that may form lymphoid follicles, eosinophils
*Cats may develop fibrosarcomas secondary to vaccination
*Dogs, especially poodles, may develop lymphoplasmacytic panniculitis and perivasculitis, vasculitis and follicular atrophy secondary to killed rabies vaccine
===Intertrigo===
*Also called '''skin fold dermatitis'''
*Develops due to irritation and bacteria in areas of skin friction and moisture (tears, saliva, glandular secretions, urine)
*Areas affected are commonly facial fold in brachycephalic breeds, [[Lips - Anatomy & Physiology|lip]] fold, body fold, vulvular fold (obese females), tail fold (corkscrew tails)
*Cows with large, pendolous udder may become affected in area between thigh and udder
**In severe cases, skin and subcutis may slough
===Pyotraumatic dermatitis===
*Also called '''acute moist dermatitis''' or ''''hot spot''''
*Common in dogs, especially self-inflicted due to pain and itching
*Usual causes: [[Skin - immunologic|allergies]], irritants, matted hair, [[Skin - infectious|parasites]]
*Lesions tend to be worse in hot and humid weather
*Grossly:
**Hairless, red and moist lesion
**Fluid exudate
**Edges are circumscribed and red
*Microscopically:
**Superficial erosive to ulcerative exudative dermatitis
**May be deeper suppurative folliculitis
===Radiation damage===
*Cells sensitive to radiation include [[Skin Glossary - Pathology|anagen]] hair follicles, germinal basal cells, melanocytes and endothelial cells
*Early changes:
**Erythema, epidermal blisters and oedema, erosions and ulceration
**Healed by scarring, hyperpigmentation with lower doses and hypopigmentation with higher doses
**Temporary or permanent alopecia
*Chronic changes:
**Scarring, altered pigmentation, alopecia
**Epidermal and adnexal atrophy
**Degeneration of vascular and elastic tissue
**Fibrosis of dermal and subcutaneous tissue
**Ulceration
**In severe damage, squamous cell carcinoma may develop
===Low temperature damage===
*Prolonged cold can cause ice crystal formation and vascular injury resultic in damage to tissue due to increased intracellular salt concentration
*Slow chilling can cause vasoconstriction, cellular damage -> secondary vasodilation and increased permeability -> oedema
*Severe and persistent cold causes vasoconstriction, increase in blood viscosity and tissue anoxia
*Lesions may occur in wet or hypoglycaemic neonates or animals recently moved from warm to cold environment
*Areas affected are extremities
*Lesions consist of [[General Pathology - Necrosis#Gangrene|gangrene]] and necrotic tissue
===High temperature damage===
*May result from excessive heat, liquids, flames, friction, lightning, electricity
*Partial or full thickness burns (first, second and third degree burns)
*Full thickness burns:
**Total destruction of skin and adnexa
**Has to be repaired by grafting
**Life threatening
*Partial thickness burns:
**Some structures preserved -> regeneration may occur
**Grossly:
***Erythema (capillary dilation)
***Oedema (increased permeability of capillaries)
***Vesicles
**Microscopically:
***[[General Pathology - Necrosis#Coagulation Necrosis|Coagulation necrosis]] of epidermis
***Subepidermal vesiculation
***Necrosis of adnexa
***Degenerated subepidermal collagen
***May involve large numbers of neutrophils if secondary ifection is present
==Sunlight damage==
*Transient erythema may develop into sunburn erythema (warmth, swelling, pain)
*Diffusion of inflammatory mediators (''e.g.'' cytokines) from damaged keratinocytes and endothelial cells
*Photooxidation of existing melanin -> pigment darkening
*Melanogenesis
*Immune responses of skin are reduced by UV light
===Solar dermatosis and neoplasia===
*Caused by chronic sunlight damage
*Damaged tissue generates free radicals than may damage nucleis acids and proteins
*If damage repaired prior to mitosis - no lasting effect
*If mitosis occurs before repair, post-mitotic repair is prone to faults and DNA mutations may result in neoplasia
===Solar dermatitis===
*Particularly in white animals and where little or no hair is present
*Grossly:
**[[Skin Glossary - Pathology|Erythema, scaling and crusting]]
**-> Wrinkled nand thickened skin
** Squamous cell carcinoma or haemangiosarcoma/haemangioma may develop
*Microscopically:
**Dyskeratotic cells
**Intercellular oedema
**Vacuolated keratinocytes
**Followed by [[Skin Glossary - Pathology|hyperkeratosis, parakeratosis and acanthosis]]
**Endothelial swelling
**Haemorrhage
**Hyperplasia
**Dermal fibrosis
**Dogs may develop actinic [[Skin Glossary - Pathology|comedones]]
===Photosensitisation===
*'''Primary'''
**Ingestion of photodynamic substance from plants (''Hypericum perforatum'' and ''Fagopyrum sagittatum'' - buckwheat) or fungal contaminants
**Induced by drug administration - phenothiazines, tetracyclines, thiazides, sulphonamides
*'''Abnormal porphyrin metabolism'''
**Bovine congenital porphyria
**Bovine erythropoeitic protoporphyria
*[[Liver - General Pathology#Photosensitisation|'''Hepatogenous''']]
**Impaired excretion of phylloerythrin (chlorophyl metabolism product) due to hepatic disease
**[[Liver - Biliary Tract#Obstruction|Biliary obstruction]]
**Inherited defects
**Hepatic injury due to toxic plants or fungal contaminants, chemicals or some infectious agents
*Grossly:
**In areas lacking hair or pigment
**Erythema, oedema -> blisters, exudation, necrosis, sloughing or keratitis
*Microscopically:
**Subepidermal vesicles
**Ulceration
**Secondary infection
===Photoenhanced dermatoses===
*Many [[Skin - immunologic|immune-mediated]] cutaneous disease are made worse by sunlight
**Lupus erythematosus
**Dermatomyositis
**Pemphigus erythematosus
*Vasculitis in extremities, especially white-haired horses
*Grossly:
**Erythematous, well circumscribed crusted lesions or hyperkeratotic [[Skin Glossary - Pathology|plaques]]
*Microscopically:
**Vasculitis of superficial dermal vessels
**Thrombi may be seen
|backcolour = FFCCCC
|linkpage =Integumentary System - Pathology
|linktext =Integumentary System
|maplink = Integumentary System (Content Map) - Pathology
|pagetype =Pathology
}}
<br>
==Chemical damage==
===Contact dermatitis===
*Results due to exposure to chemicals (not immunologic reaction)
**Acids, alkali, detergents, irritant plants ''etc.''
*In cats and dogs lesions usually on skin of abdomen, feet, chest, eyelids, axillae
*In horses lesions on muzzle, lower limbs, under tack
*Grossly:
**Erythematous [[Skin Glossary - Pathology|pathes and papules]]
**Occasionally [[Skin Glossary - Pathology|vesicles]]
**Lesions caused by self-trauma include [[Skin Glossary - Pathology|ulcers and crusts]]
*Microscopically:
**Hyperplastic, spongiotic dermatitis
**Superficial perivascular inflammation
**Necrosis may be caused by corrosive substances
===Ergot poisoning===
*Caused by ingestion of grains or grass contaminated by fungus ''Claviceps purpurae''
*Affects especially cattle
*Toxic alkaloids damage capillary endothelium, peripheral arterial and venous constriction -> thrombosis and possible tissue ischaemia
*Clinical signs develop about a week after consumption
*Grossly:
**Red and swollen extremities
**[[General Pathology - Necrosis#Dry Gangrene|Dry gangrene]] may develop on pinnae and tail
===Fescue poisoning===
*Caused by excessive consumption of ''Festuca arudinacea''
*Clinical signs develop about two weeks after consumption
*Grossly:
**[[General Pathology - Necrosis#Dry Gangrene|Dry gangrene]] of extremities
**Similar to [[Skin - environmental#Ergot poisoning|ergot poisoning]]
===Selenium poisoning===
*Caused by ingestion of plants that have accummulated excessive amounts of selenium
*May affect any herbivore, possibly also pigs
*Acute poisoning:
**Multiple organ systems are involved
*Chronic poisoning
**Poor hair quality, partial alopecia
**Horses - loss of main and tail hair, deformed hooves that may be shed
==Physical damage==
===Acral lick dermatitis===
*Also called '''lick granuloma''' or '''neurodermatitis'''
*Mostly occurs in dogs due to constant licking or chewing
*Areas most affected are carpal, metacarpal, metatarsal, radial or tibial areas
*Usually a single lesion
*Grossly:
**Circumscribed hairless areas that may ulcerate
*Microscopically:
**Compact [[Skin Glossary - Pathology|hyperkeratosis]]
**Hyperplasia of follicular and epidermal epithelium and sebaceous glands
**Collagenous fibres causing dermal thickening
**Perivascular and periadnexal plasma cell accumulation
**May be associated with mild snsory polyneuropathy
===Feline psychogenic alopecia===
*Occurs in cats
*Broken hairs cused by persistent licking -> partial alopecia
*Areas mostly affected: dorsal midline, perineal, genital, medial thigh, abdomen
*Microscopically:
**Usually normal skin
**Possibly increased [[Skin Glossary - Pathology|telogen]] follicles
===Callus===
*Hypertrophy of epidermis, particularly at pressure points
*Usually affects giant breed dogs and pigs kept on hard floor
*May be followed by folliculitis, [[Skin Glossary - Pathology|furunculosis]] and ulceration
*Microscopically:
**[[Skin Glossary - Pathology|Hyperkeratosis and acanthosis]] or epidermis and follicular epithelium
**[[Skin Glossary - Pathology|Comedones]] and follicular cysts may be present, potentially rupture and cause secondary pyoderma
**Excessive keratin widening follicular openings
===Injection site reaction===
*May be caused by subcutaneous injections
*Granulomatous nodules form with central necrotic and foreign material
*Macrophages and multinucleated giant cells around the centre
*Surrounded by granulation tissue, perivascular lymphocytes that may form lymphoid follicles, eosinophils
*Cats may develop fibrosarcomas secondary to vaccination
*Dogs, especially poodles, may develop lymphoplasmacytic panniculitis and perivasculitis, vasculitis and follicular atrophy secondary to killed rabies vaccine
===Intertrigo===
*Also called '''skin fold dermatitis'''
*Develops due to irritation and bacteria in areas of skin friction and moisture (tears, saliva, glandular secretions, urine)
*Areas affected are commonly facial fold in brachycephalic breeds, [[Lips - Anatomy & Physiology|lip]] fold, body fold, vulvular fold (obese females), tail fold (corkscrew tails)
*Cows with large, pendolous udder may become affected in area between thigh and udder
**In severe cases, skin and subcutis may slough
===Pyotraumatic dermatitis===
*Also called '''acute moist dermatitis''' or ''''hot spot''''
*Common in dogs, especially self-inflicted due to pain and itching
*Usual causes: [[Skin - immunologic|allergies]], irritants, matted hair, [[Skin - infectious|parasites]]
*Lesions tend to be worse in hot and humid weather
*Grossly:
**Hairless, red and moist lesion
**Fluid exudate
**Edges are circumscribed and red
*Microscopically:
**Superficial erosive to ulcerative exudative dermatitis
**May be deeper suppurative folliculitis
===Radiation damage===
*Cells sensitive to radiation include [[Skin Glossary - Pathology|anagen]] hair follicles, germinal basal cells, melanocytes and endothelial cells
*Early changes:
**Erythema, epidermal blisters and oedema, erosions and ulceration
**Healed by scarring, hyperpigmentation with lower doses and hypopigmentation with higher doses
**Temporary or permanent alopecia
*Chronic changes:
**Scarring, altered pigmentation, alopecia
**Epidermal and adnexal atrophy
**Degeneration of vascular and elastic tissue
**Fibrosis of dermal and subcutaneous tissue
**Ulceration
**In severe damage, squamous cell carcinoma may develop
===Low temperature damage===
*Prolonged cold can cause ice crystal formation and vascular injury resultic in damage to tissue due to increased intracellular salt concentration
*Slow chilling can cause vasoconstriction, cellular damage -> secondary vasodilation and increased permeability -> oedema
*Severe and persistent cold causes vasoconstriction, increase in blood viscosity and tissue anoxia
*Lesions may occur in wet or hypoglycaemic neonates or animals recently moved from warm to cold environment
*Areas affected are extremities
*Lesions consist of [[General Pathology - Necrosis#Gangrene|gangrene]] and necrotic tissue
===High temperature damage===
*May result from excessive heat, liquids, flames, friction, lightning, electricity
*Partial or full thickness burns (first, second and third degree burns)
*Full thickness burns:
**Total destruction of skin and adnexa
**Has to be repaired by grafting
**Life threatening
*Partial thickness burns:
**Some structures preserved -> regeneration may occur
**Grossly:
***Erythema (capillary dilation)
***Oedema (increased permeability of capillaries)
***Vesicles
**Microscopically:
***[[General Pathology - Necrosis#Coagulation Necrosis|Coagulation necrosis]] of epidermis
***Subepidermal vesiculation
***Necrosis of adnexa
***Degenerated subepidermal collagen
***May involve large numbers of neutrophils if secondary ifection is present
==Sunlight damage==
*Transient erythema may develop into sunburn erythema (warmth, swelling, pain)
*Diffusion of inflammatory mediators (''e.g.'' cytokines) from damaged keratinocytes and endothelial cells
*Photooxidation of existing melanin -> pigment darkening
*Melanogenesis
*Immune responses of skin are reduced by UV light
===Solar dermatosis and neoplasia===
*Caused by chronic sunlight damage
*Damaged tissue generates free radicals than may damage nucleis acids and proteins
*If damage repaired prior to mitosis - no lasting effect
*If mitosis occurs before repair, post-mitotic repair is prone to faults and DNA mutations may result in neoplasia
===Solar dermatitis===
*Particularly in white animals and where little or no hair is present
*Grossly:
**[[Skin Glossary - Pathology|Erythema, scaling and crusting]]
**-> Wrinkled nand thickened skin
** Squamous cell carcinoma or haemangiosarcoma/haemangioma may develop
*Microscopically:
**Dyskeratotic cells
**Intercellular oedema
**Vacuolated keratinocytes
**Followed by [[Skin Glossary - Pathology|hyperkeratosis, parakeratosis and acanthosis]]
**Endothelial swelling
**Haemorrhage
**Hyperplasia
**Dermal fibrosis
**Dogs may develop actinic [[Skin Glossary - Pathology|comedones]]
===Photosensitisation===
*'''Primary'''
**Ingestion of photodynamic substance from plants (''Hypericum perforatum'' and ''Fagopyrum sagittatum'' - buckwheat) or fungal contaminants
**Induced by drug administration - phenothiazines, tetracyclines, thiazides, sulphonamides
*'''Abnormal porphyrin metabolism'''
**Bovine congenital porphyria
**Bovine erythropoeitic protoporphyria
*[[Liver - General Pathology#Photosensitisation|'''Hepatogenous''']]
**Impaired excretion of phylloerythrin (chlorophyl metabolism product) due to hepatic disease
**[[Liver - Biliary Tract#Obstruction|Biliary obstruction]]
**Inherited defects
**Hepatic injury due to toxic plants or fungal contaminants, chemicals or some infectious agents
*Grossly:
**In areas lacking hair or pigment
**Erythema, oedema -> blisters, exudation, necrosis, sloughing or keratitis
*Microscopically:
**Subepidermal vesicles
**Ulceration
**Secondary infection
===Photoenhanced dermatoses===
*Many [[Skin - immunologic|immune-mediated]] cutaneous disease are made worse by sunlight
**Lupus erythematosus
**Dermatomyositis
**Pemphigus erythematosus
*Vasculitis in extremities, especially white-haired horses
*Grossly:
**Erythematous, well circumscribed crusted lesions or hyperkeratotic [[Skin Glossary - Pathology|plaques]]
*Microscopically:
**Vasculitis of superficial dermal vessels
**Thrombi may be seen