History: Acanthosis nigricans is traditionally characterized by symmetrical, hyperpigmented, velvety plaques that may occur in almost any location but most commonly appear on the intertriginous areas of the axillae, groins, and posterior neck. Skin tags often are found in and around the affected areas.  Hyperinsulinemia, a consequence of insulin resistance, stimulates the formation of these characteristic plaques in obesity associated acanthosis nigricans.