Skin Congenital and Hereditary - Pathology
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Acanthosis Nigricans
- Occurs in Dachshunds
- Bilateral axillary hyperpigmentation, lichenification, alopecia
- May be followed by secondary pyoderma or seborrhea
- Microscopically:
- Thickened epidermis by mainly acanthosis
- Hyperkeratosis
- Increased melanin in epidermis
Alopecia and Hypotrichosis
- Occurs in most species
- Bred for in some breeds, e.g. Mexican hairless dog, Sphinx cat
- May be due to decreased number of hair follicles, failure of hair growth or follicular dysplasia
- Also associated with maternal deficiency of iodine
Collagen Dysplasia
- Occurs in many species
- Very stretchy and loose skin that tears easily
- Due to variety of defects of enzyme necessary for collagen synthesis or processing
- Histologically:
- Varies depending on cause
- May appear normal
- Collagen bundles varied in shape, size and their organisation
Epidermolysis Bullosa
- Also called Red Foot Disease
- Occurs in sheep, dogs, cattle and horses
- Development of cutaneous blisters
- Varies depending on hereditary cause
- Affected animals tend not to survive
- Lesions appear at surfaces that are easily damaged, e.g. oral mucosa, feet
- Microscopically:
- Epidermal vesicular disease
- Healing displaces lesions more dorsally
- May become infected and form pustules
Epitheliogenesis Imperfecta
- Also called Aplasia Cutis
- Incomplete development of squamous epithelium and adnexa of skin and epithelium of oral mucosa
- Occurs in most species
- Grossly:
- Circumscribed areas of missing squamous epithelium
- Unprotected underlying tissue gets easily damaged and infected, possibly resulting in bacteraemia
Hypertrichosis
- Increased hair growth
- Both congenital or hereditary
- In sheep may be caused by Border Disease virus
- Microscopically:
- Enlarged primary follicles and wool fibres
- Also accociated with maternal hyperthermia
Ichthyosis
- Inherited cutaneous disease
- Occurs in dogs and cattle
- Grossly:
- Thickened skin due to hyperkeratosis
- May crack resembling fish scales
- Increased adherence of keratocytes preventing normal desquamation
- In cattle occurs in two forms:
- Ichthiosis fetalis - fatal, stillborn calves or die within days of birth
- Ichthiosis congenita - folded and thickened skin, fissures and partial alopecia
Photosensitisation
- May be due to inherited defects
- See HERE
Porcine Juvenile Pustular Psoriasiform Dermatitis
- Also called Pityriasis Rosea
- Occurs in pigs
- Symmetric lesions on the abdomen, loin and medial thigh
- Start as small papules covered by brown crusts
- -> lesions join and spread -> umbilicated plaques containing white centres with erythematous and scaly borders
- Similar to dermatophytosis
- Histologically:
- Epidermal hyperplasia, parakeratosis, epidermal pustules and superficial perivascular dermatitis
- For more detail see Porcine Juvenile Pustular Psoriasiform Dermatitis
- Occurs in Bullterriers and calves
- Resolves with zinc supplementation in calves but not dogs
- In dogs:
- Fatal acrodermatitis
- Lesions start between digits and on foot pads -> severe interdigital pyoderma -> paronychia and hyperkeratosis of pads
- May also occur on pinnae, elbows, muzzle, hocks or become generalised with crusting, ulceration and secondary pyoderma
- Histologically:
- Hyperkeratosis and bacterial pustular dermatitis