Several ear margin dermatoses characterized by alopecia have been described in dogs. Periodic pinnal alopecia in Miniature Poodles is characterized by progressive bilateral alopecia of the convex surfaces of the ear. The hair loss is acute in onset and progresses over several months, but hair may spontaneously regrow. There are no other clinical signs. Treatment is unnecessary.
Pinnal alopecia has been reported in Dachshunds, Chihuahuas, Italian Greyhounds, and Whippets and is thought to have a hereditary predisposition. The age of onset is ≤1 yr of age. Lesions start as thinning of the hair coat, and complete pinnal alopecia may occur by 8–9 yr of age. Other commonly affected areas are the ventral neck and thorax and the caudal medial thighs. The hair loss is asymptomatic. Differential diagnoses for this condition are endocrinopathies (eg, hypothyroidism, hyperadrenocorticism, sex hormone imbalance). Histologically, the skin is normal, and hair follicles are diminished in size but normal in appearance. No effective treatment has been reported, but pentoxifylline (10–15 mg/kg, bid-tid), melatonin (3 mg for small breeds and 6 mg for large breeds, bid-tid), and topical minoxidil have anecdotally been described as helpful.
Last full review/revision July 2011 by Sheila Torres, DVM, PhD, DACVD; Scott A. Dee, DVM, MS, PhD, DACVM