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KEY POINTS
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Acanthosis nigricans (AN) is the term used for thickened, darkened skin on the neck or in body folds, such as under the arms.
You are more likely to have AN if:
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 or already have 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.
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.
AN usually develops very slowly over many months. If your skin darkens suddenly over a couple or few weeks, you need to see your health care provider.
Your healthcare provider will ask about your symptoms and medical history and examine you. Tests may include:
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 healthier 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.
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:
Make sure you know when you should come back for a checkup.
The best way to try to prevent AN 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.