Transmission or cause: A breed-related acne-like keratinization disorder causing dilation of hair follicles on the back of miniature schnauzers.

Clinical signs: In mildly affected animals, the only sign is the formation of asymptomatic comedones (blackheads) which are dilated hair follicles on the midline of the back. In more severely affected dogs, secondary bacterial infection may develop, causing crusts, pimples, hairloss and itching.

Diagnosis: Breed and clinical signs are suggestive, but other causes of comedones such as bacterial infection, demodex and dermatophyte (ringworm) need to be ruled out with skin scrapings and cytology, and possibly fungal cultures. Additionally in older dogs, hormonal diseases such as Cushing’s disease and hypothyroidism can also cause comedones and may be diagnosed by blood testing.

Treatment: In mildly affected animals, topical treatment with human acne pads or benzoyl peroxide gel periodically may be helpful. Antiseborrheic shampoos (sulfur/salicylic acids or, in severe cases, benzoyl peroxide) may be helpful for more extensive lesions. Treatment of any secondary bacterial infection with antibiotics is also important. Severely affected dogs may benefit from oral reinoids (ie. acitretin).

Prognosis: Good, as this is a cosmetic disorder in most dogs which can be controlled (but not cured) with symptomatic topical therapy.