A Suspected Case of Hyperkeratotic Head and Neck Malassezia Dermatosis Presenting with Acanthosis Nigricans

Abstract

A 19-year-old woman presented with an asymptomatic cutaneous discoloration on her nape. Dermatological examination revealed localized dark brown to dark pigmented velvety macules and patches. She denied a past medical history, except for a 7-kg weight gain over a 6-months period. Histopathologically, the specimen showed hyperkeratosis, epidermal hyperplasia, mild acanthosis, and papillomatosis. In addition, keratin material and fungal spore were noted between the papilloma ridges. Periodic acid-Schiff special stain showed a positive result for the fungal spore in the horny layer. She was treated with a daily oral dose of terbinafine and topical flutrimazole. After 12 weeks of treatment, she is currently under observation without pigmentation and adverse effect. We considered the initial diagnosis as acanthosis nigricans because of weight gain, similar clinical features, and histological findings. However, the final diagnosis was hyperkeratotic head and neck Malassezia dermatosis considering the presence of yeast and the dramatic improvement after antifungal treatment. To the best of our knowledge, hyperkeratotic head and neck Malassezia dermatosis is not well characterized in the literature. It is an unusual variant of pityriasis versicolor. The skin lesion appears brown to dark, scaly, and hyperkeratotic macules and patches located on the face and neck. Here, we reported an unusual case of hyperkeratotic head and neck Malassezia dermatosis.