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Differentiating Keratinization Disorders

Clinician's Brief (Capsule)


|May 2014

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Keratinization defects in dogs and cats are characterized by abnormal haircoats with concurrent scaling and crusting. In this cases series, 3 dogs with similar skin biopsy findings were described. Although the dogs were first examined as adults, signs first appeared when they were puppies. The haircoat was reported to be dry, dull, and brittle with progressive scaling, hair casts, and hair loss. Two of 3 dogs for which follow-up was available responded to topical shampoo therapy combined with topical emollients (propylene glycol spray). One dog was treated with concurrent oral vitamin A and another with evening primrose oil.


Clinically, the dogs in this case series were indistinguishable from other dogs with whole-body keratinization disorders. In addition to starting when young, another interesting finding was that lesions tended to start on the head, with the earliest clinical finding being ear margin scaling and matting of the hairs on the ears. Lesions progressively spread over the body and hair casts; poor coat quality and hypotrichosis developed. One important differential for young dogs is granulomatous sebaceous adenitis (SA). Skin biopsy can help differentiate the 2 diseases, but it is important to take several samples at various body places to ensure the pathologist has adequate tissue. In SA, key findings depend on whether samples are taken early or late in the disease process. If taken early, the classic inflammatory response obscuring the sebaceous glands may be seen. If samples are obtained after this inflammatory response, sebaceous glands are described as absent. In contrast, the glands are present in sebaceous gland dysplasia but are irregularly clustered, irregular in shape and orientation, and smaller. Clients may ask why the differentiation is important; with SA, some dogs respond to cyclosporine. In my experience, response can take up to 12–16 weeks.—Karen A. Moriello, DVM, DACVD


Scaling dermatosis in three dogs associated with abnormal sebaceous gland differentiation. Peters-Kennedy J, Scott DW, Loft KE, Miller WH. VET DERMATOL 25:23-e8, 2014.

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