Benign acanthosis nigricans

**Definition:** Benign acanthosis nigricans is a thickening and pigmentation affecting predominantly flexural skin, especially the neck, axillae and groins. It is thought to be due to high concentrations of insulin binding to insulin-like growth factor receptors, with resultant keratinocyte proliferation. It is strongly associated with insulin resistance and obesity. Type 2 diabetes and the metabolic syndrome are commonly associated.

**Exclusions:** - Paraneoplastic acanthosis nigricans