Congenital hypotrichosis in a Percheron draught horse

A blue roan Percheron foal was born with poorly circumscribed patchy alopecia of the trunk and legs. Teeth and hoof development were normal. Alopecia was progressive, becoming almost complete by 1 year of age. Histopathological findings in a skin biopsy obtained at 7 months of age were consistent with severe follicular hypoplasia. Sebaceous glands, epitrichial sweat glands and arrector pilae muscles were normal. The horse is alive and otherwise well at 6 years of age, although adult stature is considered small for this breed. The clinical history and histopathological findings are most consistent with a form of congenital hypotrichosis.