Line 1: |
Line 1: |
− | | + | #REDIRECT[[:Category:Integumentary System - Environmental Pathology]] |
− | ==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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Chemical Damage]]
| |
− | ===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
| |
− | **[[Necrosis - Pathology#Dry Gangrene|Dry gangrene]] may develop on pinnae and tail
| |
− | | |
− | [[Category:Integumentary System - Chemical Damage]]
| |
− | | |
− | | |
− | ===Fescue poisoning===
| |
− | *Caused by excessive consumption of ''Festuca arudinacea''
| |
− | *Clinical signs develop about two weeks after consumption
| |
− | *Grossly:
| |
− | **[[Necrosis - Pathology#Dry Gangrene|Dry gangrene]] of extremities
| |
− | **Similar to [[Skin Environmental - Pathology#Ergot poisoning|ergot poisoning]]
| |
− | | |
− | [[Category:Integumentary System - Chemical Damage]]
| |
− | | |
− | ===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 mane and tail hair, deformed hooves that may be shed
| |
− | | |
− | [[Category:Integumentary System - Chemical Damage]]
| |
− | | |
− | ==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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | ===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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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|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
| |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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 - Pathology|allergies]], irritants, matted hair, [[Parasitic skin infections - Pathology|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
| |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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
| |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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 [[Necrosis - Pathology#Gangrene|gangrene]] and necrotic tissue
| |
− | | |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | | |
− | ===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:
| |
− | ***[[Necrosis - Pathology#Coagulation Necrosis|Coagulation necrosis]] of epidermis
| |
− | ***Subepidermal vesiculation
| |
− | ***Necrosis of adnexa
| |
− | ***Degenerated subepidermal collagen
| |
− | ***May involve large numbers of [[Neutrophils|neutrophils]] if secondary ifection is present
| |
− | | |
− | | |
− | [[Category:Integumentary System - Physical Damage]]
| |
− | | |
− | ==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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Sunlight Damage]]
| |
− | | |
− | | |
− | ===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
| |
− | | |
− | | |
− | [[Category:Integumentary System - Sunlight Damage]]
| |
− | | |
− | | |
− | ===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]]
| |
− | | |
− | [[Category:Integumentary System - Sunlight Damage]]
| |
− | | |
− | ===[[Photosensitisation]]===
| |
− | | |
− | ===Photoenhanced dermatoses===
| |
− | *Many [[Skin Immunologic - Pathology|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
| |
− | | |
− | [[Category:Integumentary System - Sunlight Damage]]
| |