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