FC‐11 Histopathology of alopecia X

Abstract

Dogs with endocrinopathy have been reported to have hair follicles with excessive trichilemmal keratinization (flame follicles). These follicles have been described in cases clinically diagnosed as hypothyroidism, hyperadrenocorticism, hyposomatotropism and sex hormone abnormality. Breed variation in the incidence of these follicles has also been described. Recently, endocrine alopecias have been better defined, and a number of these conditions (previously known as congenital adrenal hyperplasia, pseudo‐Cushing's disease, castration‐responsive dermatosis and adult‐onset hyposomatotropism) are now grouped under the name alopecia X. In this prospective study, a group of 24 spitz‐type dogs, which included 15 Pomeranians, had an extensive hormonal work‐up. This included thyroid and adrenocorticotrophic hormone stimulation tests and sex hormone assays. Histopathology of the skin specimens collected from alopecic and clinically normal skin indicated features common to many endocrinopathies such as surface and infundibular hyperkeratosis and comedone formation. However, catagenization with flame follicle formation was a prominent feature of skin specimens from 22 dogs. This feature was so marked in 20 of these specimens that it was considered to be diagnostic for alopecia X when the specimens were evaluated in a blinded manner. The other two specimens could not be differentiated reliably from hyperadrenocorticism. Histopathology is a useful diagnostic procedure to support a diagnosis of alopecia X in dogs. Funding: Self‐funded.