What is acanthosis nigricans?
Acanthosis nigricans 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 starting to have type 2 diabetes. If you have AN, it’s 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. Much less commonly it can be associated with other illnesses, including cancer.
What are the symptoms?
You have a painless area of darkened, slightly raised skin. The skin may feel velvety. In rare cases it may itch. As it develops over weeks, it may make the skin look dirty.
How is it diagnosed?
Your healthcare provider will examine your skin and ask about your symptoms and family medical history. You may have lab tests to look for signs of diabetes or other health problems that might cause AN. If there is any question about what it is, you may have a skin biopsy. When you have a biopsy, you are given a numbing medicine and then your provider removes a small piece of skin. The skin sample is sent to a lab, where it is examined under a microscope.
How is it treated?
There is no specific treatment. If AN is caused by an illness, like diabetes, treating the illness AN to go away with treatment of the illness. When AN seems to be a side effect from a medicine, your provider may prescribe a different medicine. If you have the inherited form of AN (called familial acanthosis nigricans), a cream or lotion for the skin, prescribed by your healthcare provider, may be helpful.