Acanthosis nigricans (AN) is a skin disorder in which there is darker, thick, velvety skin in body folds and creases.
AN; Skin pigment disorder - acanthosis nigricans
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 disorders, such as diabetes, obesity
- 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
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
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, however, 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.
Habif TP. Cutaneous manifestations of internal disease. In: Habif TP, ed. Clinical Dermatology. 6th ed. Philadelphia, PA: Elsevier; 2016:chap 26.
Patterson JW. Miscellaneous conditions. In: Patterson JW, ed. Weedon's Skin Pathology. 4th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2016:chap 19.