Acanthosis nigricans (OMIM ID % 100600) is a dermatosis characterized by velvety hyperpigmentation, skin thickening, and papillomatosis. It mainly affects flexural areas. In most cases, the generalized form is related to malignancy in adults; it is rarely reported in the absence of systemic disease in children and adolescents. The present report is aimed at describing an unusual case of generalized acanthosis nigricans in a 17 year-old patient, in which, after extensive investigation (clinical, laboratorial and by imaging methods) no association with systemic disease was found.