Sebaceous adenitis
- Epidermal growth or differentiation disorder
- 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. discoid lupus erythematosus
Hyperpigmentation
Image of endocrine hyperpigmentation from Cornell Veterinary Medicine
- Results from irritation or inflammation, pigmented neoplasms or metabolic diseases
- Lentigo - circumscribed macular or slightly raised plaque with epidermal hyperplasia and hyperpigmentation
Eosinophilic infiltration
Eosinophilic plaques
- Common in cats
- Medial thighs and abdomen mostly involved
- Often associated with hypersensitivity
- Grossly:raised plaques, erythematous, pruritic, erosed or ulcerated
- Microscopically: acanthosis, spongiosis, erosions or ulceration, predominantly eosinophilic dermatitis, possibly areas of collagen degeneration
Eosinophilic granulomas
- Involves cats, dogs, horses
- Collagen degeneration in lesions os eosinophil degranulation
- Often involved in reaction to parasites, foreigh bodies or mas cell tumours
- Grossly:
- Papules, nodules, plaques, ulcers in skin
- Nodules or ulcers in oral mucosa of cats and dogs or on foot pads of cats
- Microscopically:
- Nodular dermatitis or stomatitis
- Fragments of degenerated collagen surrounded by eosinophils and macrophages
Eosinophilic folliculitis and furunculosis
- Rare in cats, dogs, cattle and horses
- Possibly due to arthropod bites
- May be multifocal in horses
Sterile granulomatous disorders
Juvenile pyoderma
- Also known as Juvenile sterile granulomatous dermatitis and lymphadenitis, juveline cellulitis, puppy strangles
- Involves dogs of less then 4 months of age
- Grossly: pustular and nodular dermatitis with oedema involving the face, ears, mucocutaneous junctions
- Microscopically: granulomatous or pyogranulomatous perifolliculitis, paniculitis and dermatitis
Equine generalised granulomatous disease
- Also known as Sarcoidosis
- In horses
- Rare
- Involves cutaneous lesions and systemic disease causing anorexia and weight loss
- Grossly: alopecia, scales, crusts, sometimes nodules and masses
- Microscopically: multifocal granulomas, multinucleated giant cells