Skin Other - Pathology
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Epidermal growth or differentiation disorders
Seborrheic disease complex
- Abnormal cornification or function of sebaceous glands
- Large amounts of free fatty acids and cholesterol
- Decreased amounts of diester waxes in surface lipids
- Bacterial population changes to pathogenic coagulase positive staphylococci
- Chronic disease affecting mainly dogs, sometimes cats and horses
- Dry form - white to grey scales
- Greasy form - scaly, excess brown to yellow lipids sticking to skin and hair
Primary idiopathic seborrhea
- Abnormal cornification
- Epidermal turnover reduced to about 2/3 of normal
- Microscopically:
- Hyperkeratosis distending follicular ostia causing papillary appearance
- Parakeratosis at edges of follicular ostia
- Congested, oedematous dermal papillae
- Spongiotic epidermis with leukocytes
Secondary seborrhea
- Develops secondarily to many types of disease (e.g. ectoparasites, fungal infections, endocrine disease, internal disease or allergy)
- Microscopically:
- Hyperkeratosis and/or parakeratosis of follicles and epidermis
- Lesions relevant to the other disease
Sebaceous adenitis
- Inflammation of sebaceous glands, alopecia, hyperkeratosis
- Possibly immune-mediated
- Mainly affects dogs
- Long haired show multifocal, serpiginous and annular lesions
- Microscopically:
- Inflammation of sebaceous glands
- Possibly orthokeratotic hyperkeratosis
- Chronic lesions are deprived of sebaceous glands and contain mild inflammation and fibrosis at follicular isthmus
Pigmentation disorders
Hypopigmentation
- Leukoderma or vitiligo - loss of pigment in the skin
- Leukotrichia - loss of pigment of the hair
- Hypopigmentation or incomplete albinism - generalised reduction of pigment in skin or hair
- Albinism - inherited lack of pigment
- Dilution - reduced pigmentation
- Can be localised or generalised, idiopathic or asociated with other diseases
- Examples of hereditary conditions: Maltese dilution of cats, Chediak-Higashi syndrome, leukoderma and leukotrichia of Dobermans, Arabian fading syndrome
- Asociated with some immune-mediated disorders, e.g. [[Skin Immunologic - Pathology#Lupus|discoid lupus erythematosu