Acanthosis nigricans (AN) is a lesion affecting localized areas of the skin in persons with obesity and/or hyperinsulinemia. Biochemical mechanisms responsible for developing this hyperplastic lesion are unclear, but likely involve local cutaneous growth factors. It is associated with obesity, endocrinopathies (insulin resistance, diabetes mellitus, Cushing disease and acromegaly) and visceral malignancies. Clinicians should recognize AN because it may herald disorders ranging from endocrine disturbances to malignancy. Early recognition of these conditions is essential to identify children who are at highest risk for developing type 2 diabetes and further metabolic abnormalities.