Acanthosis nigricans

Acanthosis nigricans is a cutaneous finding characterized by brown-to-black, velvety hyperpigmentation of the skin, most often affecting body folds such as the posterior neck, axillae, groin and umbilicus. It is strongly associated with insulin resistance and hyperinsulinaemia, including in type 2 diabetes and metabolic syndrome. Excess insulin activates insulin and insulin-like growth factor signalling pathways, stimulating proliferation of keratinocytes and fibroblasts and producing the characteristic plaques.

Acanthosis nigricans may also occur in hereditary syndromes, as a reaction to medications or as a paraneoplastic syndrome associated with internal malignancy. In children, it is an important clinical marker of metabolic and cardiometabolic risk.