Ectopic presentation of hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a chronic inflammatory disease involving primarily intertriginous skin areas. Ectopic HS lesions are a reported phenomenon that is not fully understood. We present a case report of a 66-year-old patient with painful symmetric ulcerated plaques on the posterior surface of the ankles and lower lip. In addition, we performed a systematic review on ectopic HS by conducting an electronic literature search to identify relevant contributions. Inclusion criteria included English-language and full texts only using PubMed, Embase, and the Cochrane Database. We found 22 eligible contributions reporting on a total of 58 patients. Most of the patients were men who had lesions on the head and neck region. The reviewed cases share common features with HS and may be considered disorders of follicular occlusion.