Symmetrical noninflammatory alopecic disorders affecting the pinna, such as periodic pinnal alopecia, pattern baldness, and alopecia associated with melanoderma, may affect dogs and cats and are typically idiopathic.
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 throughout several months, but hair may spontaneously regrow. There are no other clinical signs. A similar condition has been reported in Siamese cats in which complete or patchy alopecia of the convex aspect of both pinna develops. Treatment is unnecessary.
Pattern baldness affecting only the pinna has been reported in Dachshunds, Chihuahuas, Italian Greyhounds, and Whippets and is thought to have a hereditary predisposition. The age of onset is ≤1 year of age. Lesions start as thinning of the hair coat, and complete pinnal alopecia may occur by 8–9 years of age. Other commonly affected areas are the ventral neck and thorax and the caudal medial thighs. The hair loss is asymptomatic. Histologically, the skin is normal, and hair follicles are diminished in size but normal in appearance. No effective treatment has been reported, but pentoxifylline (15–20 mg/kg, PO, 2 to 3 times a day) and melatonin (3 mg for small breeds and 6 mg for large breeds, 2 to 3 times a day) have been described as helpful. Pattern baldness restricted to the pinna has also been reported in cats.
Alopecia and melanoderma in Yorkshire Terriers. Clinical signs are first noticed between 6 months and 3 years of age, symmetric alopecia and marked hyperpigmentation on the pinna, and in most cases also the bridge of the nose, tail and feet are affected. The alopecic and hyperpigmented skin has a smooth, shiny, and leathery appearance. The condition tends to worsen as the dog ages, and it typically does not spontaneously resolve. There is no treatment.
