Pinnal Alopecia in Dogs and Cats

Symmetrical noninflammatory alopecic disorders affecting the pinna, such as periodic pinnal alopecia, pattern baldness, and alopecia associated with melanoderma, can 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. Hair loss is acute in onset and progresses over several months; however, hair can sometimes spontaneously regrow. There are no other clinical signs. Treatment is unnecessary.

Pattern baldness affecting only the pinna is known to occur in Dachshunds, Chihuahuas, Italian Greyhounds, and Whippets and is thought to be hereditary. The age of onset is ≤ 1 year. Lesions start as thinning of the coat, and complete pinnal alopecia can occur by age 8–9 years. Other commonly affected areas are the ventral neck and thorax and the caudal medial thighs. The hair loss is not associated with systemic clinical signs. Histologically, the skin is normal, and hair follicles are diminished in size but normal in appearance. No effective treatment has been reported. Pattern baldness restricted to the pinna has also been reported in cats (1).

Melanoderma in Yorkshire Terriers results in pinnal alopecia. Clinical signs, including symmetric alopecia and marked hyperpigmentation of the pinnae, are first noticed between the ages of 6 months and 3 years. The bridge of the nose, tail, and feet are also affected in most cases. The alopecic and hyperpigmented skin has a smooth, shiny, leathery appearance. The condition tends to worsen as the dog ages, and it typically does not spontaneously resolve. There is no treatment.