Skin Environmental - Pathology
Chemical damage
Contact Dermatitis
Ergot Poisoning
Fescue Poisoning
Selenium Poisoning
Physical damage
Acral Lick Dermatitis
Callus
Feline Psychogenic Alopecia
Injection Site Reaction
Intertrigo
Pyotraumatic Dermatitis
Radiation Damage
Low Temperature Damage
=High Temperature 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
Solar Dermatosis and Neoplasia
Solar dermatitis
- Particularly in white animals and where little or no hair is present
- Grossly:
- 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 hyperkeratosis, parakeratosis and acanthosis
- Endothelial swelling
- Haemorrhage
- Hyperplasia
- Dermal fibrosis
- Dogs may develop actinic comedones
Photosensitisation
Photoenhanced dermatoses
- Many 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 plaques
- Microscopically:
- Vasculitis of superficial dermal vessels
- Thrombi may be seen