The main sign of acanthosis nigricans is dark, thick, velvety skin in body folds and creases. It often appears in the armpits, groin and back of the neck. It develops slowly. The affected skin might be itchy, have an odor and develop skin tags.

Consult your health care provider if you notice changes in your skin — especially if the changes are sudden. You may have an underlying condition that needs treatment.

Acanthosis nigricans might be related to:

• Insulin resistance. Most people who have acanthosis nigricans have also become resistant to insulin. Insulin is a hormone secreted by the pancreas that allows the body to process sugar. Insulin resistance is what leads to type 2 diabetes. Insulin resistance is also related to polycystic ovarian syndrome and might be a factor in why acanthosis nigricans develops.
• Certain drugs and supplements. High-dose niacin, birth control pills, prednisone and other corticosteroids may cause acanthosis nigricans.
• Cancer. Some types of cancer cause acanthosis nigricans. These include lymphoma and cancers of the stomach, colon and liver.

The risk of acanthosis nigricans is higher in people who have obesity. The risk is also higher in people with a family history of the condition, especially in families where obesity and type 2 diabetes are also common.

People who have acanthosis nigricans are much more likely to develop type 2 diabetes.

Acanthosis nigricans can be detected during a skin exam. To be sure of the diagnosis, your health care provider might take a skin sample (biopsy) to look at under a microscope. Or you may need other tests to find out what's causing your symptoms.

There's no specific treatment for acanthosis nigricans. Your care provider might suggest treatments to help with pain and odor, such as skin creams, special soaps, medications and laser therapy.

Treating the underlying cause might help. Examples include:

• Lose weight. If your acanthosis nigricans is caused by obesity, nutritional counseling and losing weight may help.
• Stop medications. If your condition seems to be related to a medication or supplement that you use, your care provider may suggest that you stop using that substance.
• Have surgery. If acanthosis nigricans was triggered by a cancerous tumor, surgery to remove the tumor often clears up the skin symptoms.

You're likely to start by seeing your primary care provider. Or you may be referred to a doctor who specializes in skin disorders (dermatologist) or hormone problems (endocrinologist). Because appointments can be brief and there's often a lot to discuss, it's a good idea to prepare for your appointment.

What you can do

Before your appointment, you may want to list answers to the following questions:

• Has anyone in your family ever had these skin symptoms?
• Does diabetes run in your family?
• Have you ever had problems with your ovaries, adrenal glands or thyroid?
• What medications and supplements do you take on a regular basis?
• Have you ever had to take high doses of prednisone for more than a week?

What to expect from your doctor

Your health care provider is likely to ask you questions, such as the following:

• When did your symptoms begin?
• Have they gotten worse?
• What areas of your body are affected?
• Have you ever had cancer?