Definition

Acanthosis nigricans (AN) is a skin disorder in which there is darker, thick, velvety skin in body folds and creases.

Alternative Names

AN; Skin pigment disorder - acanthosis nigricans

Causes

AN can affect otherwise healthy people. It can also be related to medical problems, such as:

• Genetic disorders, including Down syndrome and Alström syndrome
• Hormone imbalances that occur in diabetes and obesity, often called insulin resistance
• Cancer, such as cancer of the digestive system, liver, kidney, bladder, or lymphoma
• Some medicines, including hormones such as human growth hormone or birth control pills

Symptoms

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

Your health care provider can usually diagnose AN by looking at your skin. A skin biopsy may be needed in rare cases.

If there is no clear cause of AN, your provider may order tests. These may include:

• Blood tests to check blood sugar level or insulin level
• Endoscopy
• X-rays

Treatment

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.

Outlook (Prognosis)

AN often disappears if the cause can be found and treated.

When to Contact a Medical Professional

Contact your provider if you develop areas of thick, dark, velvety skin.

References

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.