What is acanthosis nigricans?

Acanthosis nigricans (AN) is the term used for thickened, darkened skin on the neck or in body folds, such as under the arms.

What is the cause?

You are more likely to have AN if:

• You are overweight.
• You have type 2 diabetes or another hormone problem.
• It runs in your family (inherited).
• You take certain medicines, such as birth control pills.
• You have certain types of cancer.

In most cases AN is a sign that you are gaining too much weight. It is also often a sign that you are at risk for type 2 diabetes. Much less commonly it may be associated with other illnesses, including cancer. If you have AN, it’s very important to get checked for type 2 diabetes and other possible causes.

What are the symptoms?

The main symptom is a painless area of darkened, slightly raised skin that may feel velvety. Sometimes the skin may itch or have a bad odor.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and medical history and examine you. Tests may include:

• Blood and urine tests
• Biopsy, which is the removal of a small sample of skin tissue for testing

How is it treated?

Treatment of AN depends on the cause. If AN is caused by an illness, like diabetes, treating the illness may also take care of the skin problems. The skin changes often get better with the improved diet and exercise that treats or helps prevent diabetes.

If AN is a side effect from a medicine, your healthcare provider may prescribe a different medicine.

Your provider may prescribe a cream or lotion for your skin, but these creams are often not helpful. Healthcare providers who specialize in skin problems (dermatologists) can do procedures that take off the top layers of skin to try to lighten the AN. However, these treatments can cause darkening, especially if your skin is naturally brown.

How can I take care of myself?

Talk to your healthcare provider and work with him or her to find and treat the underlying cause.

Follow the full course of treatment prescribed by your healthcare provider. Ask your healthcare provider:

• How and when you will hear your test results
• How long it will take to recover
• How to take care of yourself at home
• What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for a checkup.

How can I help prevent acanthosis nigricans?

The best way to try to prevent AN that’s not the inherited type is to have a healthy weight and diet, along with regular physical activity. Together these good health habits can help prevent blood sugar problems that can lead to diabetes and AN.