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Acanthosis nigricans is a condition characterized by dark, thick areas on the skin. The areas affected are spread out, and the skin is velvety. It is most common in the armpits and other body folds.

This condition is not one disease. Rather, it is a symptom that can be caused by several different disease processes, or can occur for unknown reasons.

What is going on in the body?

There are at least four disease processes associated with acanthosis nigricans:

• Gougerot-Carteaud syndrome occurs in young females and is probably inherited.
• Malignant acanthosis nigricans is sometimes seen in adults with cancer of the genital, urinary, or gastrointestinal systems.
• Miescher syndrome is an inherited disease that causes skin lesions for no apparent reason.
• Pseudoacanthosis nigricans is caused by a hormone imbalance in the body that may cause excess insulin in the blood.

What are the signs and symptoms of the disease?

Acanthosis nigricans causes skin lesions that are darker than the skin around them. The lesions have a velvety feel. The lesions often form in the folds along the neck, armpits, groin, knuckles, between the legs, at the elbow, under the breasts, and around the belly button.

What are the causes and risks of the disease?

• Addison disease, which is caused by a deficiency of hormones from the adrenal gland
• diabetes
• disorders of the pituitary gland within the brain
• genetic causes
• growth hormone therapy
• hypothyroidism, which means low levels of thyroid hormone that are caused by decreased activity of the thyroid gland
• insulin resistance caused by obesity
• oral contraceptives
• some medicines, such as nicotinic acid, which are used to treat high cholesterol

What can be done to prevent the disease?

When acanthosis nigricans is caused by obesity, weight management is key. When it is caused by cancer, there may be little that can be done to prevent it until the cancer is successfully treated. Acanthosis nigricans caused by medicine may go away once the medicine is stopped.

How is the disease diagnosed?

A healthcare professional can diagnose acanthosis nigricans by doing a medical history and physical exam.

What are the long-term effects of the disease?

A person with acanthosis nigricans may have chafing of the skin. These areas do not become cancerous. The appearance of these chafed spots bothers some people.

What are the risks to others?

Acanthosis nigricans is not contagious and poses no risk to others.

What are the treatments for the disease?

• antibiotic ointments or creams
• retinoids, taken orally or used in a cream
• topical corticosteroid creams
• weight loss to lower insulin resistance

What are the side effects of the treatments?

Side effects of steroid creams and ointments include stretch marks and thinning of the skin. Retinoids can cause birth defects if taken by a pregnant woman.

What happens after treatment for the disease?

The healthcare professional may recommend treatment for an underlying condition or disease. For example, obese people may be advised to lose weight to lower their insulin resistance. A person who has diabetes will need to keep blood glucose levels under good control.

How is the disease monitored?

The disease or condition that is causing acanthosis nigricans will need to be monitored. Any new or worsening symptoms should be reported to the healthcare professional.