Acanthosis nigricans is a medical sign characterised by brown to black, poorly defined, velvety hyperpigmentation of the skin. It can also be due to some underlying disease, so don't ignore & consult your doctor. . . # Acanthosis nigricans is a medical sign characterised by brown to black, poorly defined, velvety hyperpigmentation of the skin. It can also be due to some underlying disease, so don't ignore & consult your doctor. . . # La glutatin peroxidasa srica se asocia a la enfermedad del hgado graso no alcohlico en nios y adolescentes Glutathione 500 mg Plus 21st Century Vitamins 21st Century Vitamins Understanding Acanthosis Nigricans and Hyperpigmentation Acanthosis nigricans, also known as Dark neck black neck, is a skin condition that causes darker, thicker skin and that may feel velvety. It usually appears on the neck, folds of the