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Acanthosis Nigricans

What is acanthosis nigricans?

Acanthosis nigricans is the name given to thickened, darkened skin that occurs on the neck, under the arms, and in skin folds.

Why does it occur?

It may occur normally in some people as an inherited form called familial acanthosis nigricans. However, it may also be a sign of illness. For example, it may be caused by:

  • hormone problems such as insulin resistance (before full-blown diabetes develops), polycystic ovary syndrome, acromegaly (overproduction of growth hormone), or Cushing's syndrome
  • some cancers.

Sometimes acanthosis nigricans happens when you take certain medicines, such as nicotinic acid, diethylstilbestrol (DES), and steroids. Most often it is a sign that type 2 diabetes is developing.

What are the symptoms?

You have a painless area of darkened, slightly raised skin. The area of skin may feel velvety. In rare cases it may itch.

How is it diagnosed?

The diagnosis is usually based on how your skin looks and where your skin is affected. If the diagnosis is uncertain, you may have a skin biopsy. When you have a biopsy, you are first given a numbing medicine. Then your provider removes a small piece of skin. The skin sample is sent to a lab. At the lab the sample is examined under a microscope.

How is it treated?

There is no specific treatment for acanthosis nigricans. If it is caused by an illness, your provider will treat the illness. When it seems to be a side effect from a medicine, your provider may prescribe a different medicine.

If you have acanthosis nigricans, it is very important to get checked for type 2 diabetes and other possible causes. The skin changes often get better with the improved diet and exercise that treats or helps prevent diabetes.

If you have the inherited form (familial acanthosis nigricans), creams put on the skin may be helpful.

How long will the effects last?

Acanthosis nigricans will last as long as the underlying cause is present. If you have insulin resistance or diabetes, the rash may improve or go away with weight loss or other treatment of the diabetes. If the acanthosis nigricans is due to cancer, then your skin may become more normal after the tumor is removed.

How can I take care of myself?

The most important thing you can do is to talk to your healthcare provider and work with him or her to determine the underlying cause.

Written by Tom Richards, MD.
Published by RelayHealth.
Last modified: 2004-04-01
Last reviewed: 2008-06-01
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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