Acanthosis nigricans is a skin disorder in which there is darker, thick, velvety skin in body folds and creases.
Acanthosis nigricans can affect otherwise healthy people, or it can be related to medical problems. Some cases are genetically inherited. The condition is most commonly seen among people of African descent, in part because it is easier to see in darker skin.
Obesity can lead to acanthosis nigricans, as can some endocrine disorders. It is often found in people with obesity-related insulin resistance.
Some medicines, particularly hormones such as human growth hormone or birth control pills, can also cause acanthosis nigricans.
People with lymphoma or cancers of the gastrointestinal or genitourinary tracts can also develop severe cases of acanthosis nigricans.
Acanthosis nigricans 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.
Less commonly, the lips, palms, soles of the feet, or other areas may be affected. These symptoms are more common in people with cancer.
Exams and Tests
Your health care provider can usually diagnose acanthosis nigricans by looking at your skin. A skin biopsy may be needed in unusual cases.
If there is no clear cause of acanthosis nigricans, your doctor may order tests. These may include:
Because acanthosis nigricans usually only changes the skin's appearance, no treatment is needed. If the condition is affecting your appearance, using moisturizers containing ammonium lactate can help improve the skin's appearance.
It is important, however, to treat any underlying medical problem that may be causing these skin changes. When acanthosis nigricans is related to obesity, losing weight often improves the condition.
Acanthosis nigricans often fades if the cause can be found and treated.
When to Contact a Medical Professional
Call your health care provider if you develop areas of thick, dark, velvety skin.
Morelli JG. Diseases of the epidermis. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, PA: Elsevier Saunders; 2007:chap. 656.
Richard J. Moskowitz, MD, dermatologist in private practice, Mineola, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.