Histological and dermatoscopic description of sphynx cat skin

Background Histological and hair coat abnormalities of the alopecic sphynx cat have not been described in detail. The hairless allele (hr) in sphynx cats represents a mutation in the gene for keratin 71, a protein expressed in the inner root sheath of humans and mice. Hypothesis/Objectives To describe the histological and dermatoscopic abnormalities of sphynx cat skin. Animals Skin biopsies were collected from 14 sphynx cats and five cats with normal coats. Dermatoscopic examinations were performed on 11 sphynx cats and six additional control cats. Methods Vertical and horizontal sections of skin biopsy samples from sphynx and control cats were reviewed. Dermatoscopic images were compared between sphynx and control cats. Results Sphynx cat hair follicles were often small, curved and kinked and demonstrated infundibular hyperkeratosis and dilatation. Changes in the inner root sheath of sphynx cats included a poorly defined Henle's layer in addition to vacuolar‐like changes and eosinophilic globules in Huxley's layer. Dermal papillae in sphynx cat anagen bulbs lacked the normal flame shape and were surrounded by epithelial cells arranged in a disorderly manner. The degree of follicular abnormalities varied between follicles. Follicular density was similar for both sphynx cats and control animals. Sphynx cat hair shafts were misshapen, smaller in diameter and rarely medullated. Dermatoscopy revealed similar hair coat density in sphynx and control cats. Conclusions and clinical importance Sphynx cats demonstrated hair follicle dysplasia, with abnormal shaft production but without a decrease in follicle quantity. Abnormalities in sphynx cat follicles are similar to those in murine KRT71 mutants and suggest abnormal hair shaft keratinization. Résumé Contexte Les anomalies cliniques et histologiques du pelage des chats sphynx alopéciques n'ont pas été décrites en détail. L'allèle sans poil (hr) chez le sphynx représente une mutation du gène de la kératine 71, une protéine exprimée dans la gaine épithéliale interne chez l'homme et la souris. Hypothèses/Objectifs Décrire les anomalies histologies et dermatoscopiques de la peau des chats sphinx. Sujets Des biopsies cutanées ont été prélevées sur 14 chats sphynx et cinq chats avec un pelage normal. Les examens dermatoscopiques ont été réalisés sur 11 chats sphynx et six chats contrôles. Méthodes Les sections verticales et horizontales des biopsies cutanées des chats contrôles et sphinx ont été examinées. Les images d