Acanthosis nigricans is a disorder that may begin at any age. It causes velvety, light-brown-to-black, markings usually on the neck, under the arms or in the groin. Acanthosis nigricans is most often associated with obesity.
Eating too much of the wrong foods, especially starches and sugars, can cause insulin resistance. This will result in elevated insulin levels. Most patients with acanthosis nigricans have a higher insulin level than those of the same weight without acanthosis nigricans. Elevated levels of insulin in most cases probably cause acanthosis nigricans. The elevated insulin levels in the body activate insulin receptors in the skin, forcing it to grow abnormally. Reducing the circulating insulin by dieting or medication can lead to improvement of the skin problem.
When acanthosis nigricans develops in people who are not overweight, a medical work-up should be done. Rarely acanthosis nigricans is associated with a tumour, most commonly of the stomach or gut. In these cases acanthosis can bee seen in extra places, such as the lips or hands and is unusually severe. Occasionally acanthosis nigricans is congenital or due to an endocrine (glandular) disorder.
Treatment to just improve the appearance includes topical treitoin, 20% urea, alpha hydroxyacids, and lactic or salicylic acid prescriptions. Regular exercise to reduce weight is most essential.