Idiopathic eruptive macular pigmentation or acanthosis nigricans?

A 21-year-old male presented with numerous asymptomatic dark brown to brown black pigmented macules and barely raised plaques on the face, trunk and extremities, developing over a period of 2 year. The surface of most lesions had a velvety raised surface similar in appearance to acanthosis nigricans and a biopsy from one of the lesions showed pigmented papillomatosis. This case fulfils all the criteria for idiopathic eruptive macular pigmentation (IEMP) with papillomatosis, and the clinical appearance of acanthosis nigricans in most lesions suggests that IEMP is a form of eruptive acanthosis nigricans.

Keywords
Acanthosis nigricans, idiopathic eruptive macular pigmentation, pigmented papillomatosis