Small Animal Dermatology Q&A 16

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A 2-year-old blue doberman pinscher dog was referred for the problem of an ‘endocrine alopecia’ of unknown etiology. Previous diagnostic tests were normal or negative and included: skin scrapings, dermatophyte culture, complete blood count, urinalysis, serum chemistry panel, thyroid hormone evaluation, low-dose dexamethasone suppression test, and surgical neutering. Dermatological examination reveals a thin hair coat, nodular-like hair follicles, comedones, bacterial pyoderma, and scaling. All of the other littermates are similarly affected.

Question	Answer		Article
What is the most likely diagnosis, and what is the cause?	Color dilution alopecia (previously called color mutant alopecia). This is a genetic disorder of the hair coat commonly associated with a blue or fawn coat color. The cause is unknown, but it is believed to be due, in part, to a defect in the coat color genes at the D locus. Affected dogs are born with normal hair coats and, as they mature, they develop hair loss on the dorsum, recurrent bacterial infections, generalized thinning of the hair coat, secondary seborrhea, and cystic or dilated hair follicles. As hairs regrow, they grow more slowly and are often deformed. This disorder has been seen in cats with blue or cream colored coats.		Link to Article
How is this disorder treated?	There is no effective treatment for this disorder. In the early stages of the disorder, hair loss is caused by hair shaft fracture. As a result, excessive grooming and harsh shampoos should be avoided. It is important to control the recurrent bacterial pyodermas associated with this disorder. Affected dogs will continue to lose hair, and many are alopecic by 2–3 years of age.		Link to Article
What are the most common histological findings?	Common histological findings show melanin clumping in the epidermal and follicular basal cells, macromelanosomes in the hair shafts or hair bulbs, and follicular dysplasia. The melanin clumping and macromelanosomes are key findings for diagnosis of this disease.		Link to Article