Acanthosis nigricans is a skin condition characterized by dark, thick, velvety skin in body folds and creases. Most often, acanthosis nigricans affects your armpits, groin and neck. Acanthosis nigricans can begin at any age. It's most obvious in people who have dark skin.
Acanthosis nigricans is often associated with conditions that increase your insulin level, such as type 2 diabetes or being overweight. If your insulin level is too high, the extra insulin may trigger activity in your skin cells. 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.
In some cases, acanthosis nigricans is inherited. Certain medications such as human growth hormone, oral contraceptives and large doses of niacin can contribute to the condition. Other hormone problems, endocrine disorders or tumors may play a role as well. Rarely, acanthosis nigricans is associated with certain types of cancer.
Characteristics of acanthosis nigricans include slow progression, possible itching and skin changes.
Slow progression. The skin changes appear slowly, sometimes over months or years.
Possible itching. Rarely, the affected areas may itch.
Skin changes. Skin changes are the only signs of acanthosis nigricans. You'll notice dark, thick, velvety skin in body folds and creases — typically in your armpits, groin and neck. Sometimes the lips, palms or soles of the feet are affected as well.
With acanthosis nigricans, you may naturally be concerned about the appearance of your skin. Some steps may help lighten the affected areas of your skin. There's no specific treatment for acanthosis nigricans but treating any underlying conditions, such as diabetes and obesity, may cause the changes in your skin changes to fade. If you're overweight, losing excess pounds can help.