Acanthosis nigricans is a skin problem that results in brown or black velvet-like markings. They appear under the arms, in the groin, or on the back of the neck. It can affect any skin fold.
Causes may be:
This problem is more common in people who are Native American, Black, or Hispanic. Other things that may raise the risk are:
Symptoms include velvety-looking, dark areas anywhere on the skin.
The doctor will ask about your symptoms and health history. A physical exam will be done. It will focus on the skin. This is often enough to make the diagnosis.
If the diagnosis is not certain, a skin biopsy may be done.
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The underlying cause will need to be treated. Some choices are:
To lower the risk of this problem:
American Academy of Dermatology
NORD—National Organization for Rare Diseases
Canadian Dermatology Association
Acanthosis nigricans. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/acanthosis-nigricans. Accessed October 29, 2020.
Phiske MM. An approach to acanthosis nigricans. Indian Dermatol Online J. 2014 Jul;5(3):239-249.
Last reviewed September 2020 by EBSCO Medical Review Board James P. Cornell, MD Last Updated: 4/28/2021