Vacuolation of hair follicles – melanocytes.
Loss of hair colour
DDX
Alopecia areata (early, with leucotrichia)
Endocrinopathy
Genodermatosis: Colour Dilute Alopecia (early, with leucotrichia)
Hypersensitivity:Cutaneous Adverse Food Reaction
Neoplasia:n Cutaneous T Cell (Epitheliotropic) Lymphoma
Nutritional deficiency
Post-inflammatory: Bacterial pyoderma; Leishmaniosis
Hyperpigmentation of eye and dermatome of trigeminal nerve – facial pigmentation.Malho P, Shea A, Donaldson D. Nevus of Ota (oculodermal melanocytosis) in a dog. Vet Ophthalmology 2017
Vitiligo is clinically a loss of pigmentation of the skin leaving white patches and regions. Histologically there is a lack of melanocytes and melanin in affected areas of epidermis and hair follicles. Many are believed to be an immune mediated attack of the melanocytes.
The breeds affected include Belgian Tervuerens (about 50% of cases), rottweilers ( about 20%), Labrador retrievers (about 9%), and German shepherd dogs (about 4%). Lesions were mostly on the face and about the lips.
Tham HL, Linder KE, Olivry T. Autoimmune diseases affecting skin melanocytes in dogs, cats and horses: vitiligo and the uveodermatological syndrome: a comprehensive review. BMC Vet Res. 2019; 15: 251.
This study documents iatrogenic hyperglucocorticism as the major cause for calcinosis cutis in 46 dogs. Endogenous hyperadrenocorticism and underlying renal disease are other, less common causes. The underlying diseases were not known in four dogs. Male dogs were over-represented and large breeds are predisposed.Doerr KA, Outerbridge CA, White SD, Kass PH, Shiraki R, Lam AT, Affolter VK. Calcinosis cutis in dogs: histopathological and clinical analysis of 46 cases. Vet Dermatol 2013; 24: 355-361
Idiopathic calcinosis cutis has no predisposing condition and has been described in puppies. It is reported to spontaneously resolve.