AN; Skin pigment disorder - acanthosis nigricans
Acanthosis nigricans (AN) is a skin disorder in which there is darker, thick, velvety skin in body folds and creases.
AN can affect otherwise healthy people. It can also be related to medical problems, such as:
AN usually appears slowly and doesn't cause any symptoms other than skin changes.
Eventually, dark, velvety skin with very visible markings and creases appears in the armpits, groin and neck folds, and over the joints of the fingers and toes.
Sometimes, the lips, palms, soles of the feet, or other areas are affected. These symptoms are more common in people with cancer.
Exams and Tests
No treatment is needed, as AN only causes a change in skin color. If the condition is affecting your appearance, using moisturizers containing ammonium lactate, tretinoin, or hydroquinone can help lighten the skin. Your provider may also suggest laser treatment.
It is important to treat any underlying medical problem that may be causing these skin changes. When AN is related to obesity, losing weight often improves the condition.
AN often disappears if the cause can be found and treated.
When to Contact a Medical Professional
Call your provider if you develop areas of thick, dark, velvety skin.
Dinulos JGH. Cutaneous manifestations of internal disease. In: Dinulos JGH, ed. Habif's Clinical Dermatology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 26.
Patterson JW. Miscellaneous conditions. In: Patterson JW, ed. Weedon's Skin Pathology. 5th ed. Philadelphia, PA: Elsevier; 2021:chap 20.
Last reviewed on: 4/10/2020
Reviewed by: Ramin Fathi, MD, FAAD, Director, Phoenix Surgical Dermatology Group, Phoenix, AZ. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.