Light brown or black skin patches may be a sign of acanthosis nigricans. This treatable skin disorder isn't contagious or dangerous. However, it can be a sign of diabetes, so talk to your healthcare provider. Often, treating diabetes (or another underlying cause) causes the skin to clear up.
What is acanthosis nigricans?
This skin disorder results in light-brown-to-black spots. It often happens to otherwise healthy people, but in some cases, it may be a sign of an underlying condition. The markings look like a spot or stain that you might think you can scrub off. But washing will not remove acanthosis nigricans (AN).
Where does acanthosis nigricans appear?
The velvety markings that are characteristic of acanthosis nigricans (a-can-THO-sis NIH-grih-cans) can appear anywhere on the body. They most often show up on the skin folds of the neck, armpits and groin and under the breasts.
Is acanthosis nigricans contagious?
No, AN isn't contagious. You can't pass it to others or get it from other people.
Is acanthosis nigricans dangerous?
The condition is not harmful, but it may be a sign of an underlying condition that requires treatment. If you notice unusual marks or skin shading, see your healthcare provider. Your provider or a dermatologist (skin specialist) will run some tests to determine what type of treatment you need.
Who gets acanthosis nigricans?
Anyone can develop acanthosis nigricans, including otherwise healthy people. You may be at higher risk for getting this condition if you:
Have excess weight or obesity.
Have a family history of AN.
Are of Native American, African, Caribbean or Hispanic descent.
Have darker skin.
Does acanthosis nigricans mean I have diabetes?
While AN doesn’t always mean you have diabetes or prediabetes, it can be a sign of diabetes. So talk to your healthcare provider if you notice signs of AN.
Prediabetes means you have early signs but haven’t yet developed diabetes. If you have prediabetes, your provider will talk to you about steps to take to reduce your risk of developing diabetes. And if you do have diabetes, you and your provider can discuss treatment options.
How common is acanthosis nigricans?
Acanthosis nigricans is a rare disease. Researchers don’t know how often it occurs in America. However, a study of adults with obesity found that of those who weighed double their ideal body weight, at least 50% showed signs of acanthosis nigricans.
What causes acanthosis nigricans?
AN can have many causes, including:
Conditions associated with elevated insulin blood level, such as obesity, prediabetes or diabetes.
Congenital cause, meaning you are born with this condition.
Genetics, if family members have AN as well.
Certain medications, such as birth control pills or steroids.
Hormonal conditions, including thyroid disease, Addison’s disease, hypothyroidism or other pituitary disorders.
Growth hormone therapy.
AN symptoms tend to develop slowly. If symptoms develop quickly, it may be a sign of cancer, though this is rare.
What are symptoms of acanthosis nigricans?
Signs of this skin condition include:
Patches of brown or black skin.
Skin that feels velvety.
Foul-smelling skin patches.
Symptoms tend to appear slowly, over months or even years. If these signs appear suddenly, see a dermatologist. It may be a sign of cancer.
How is acanthosis nigricans diagnosed?
Your healthcare provider will talk to you about your symptoms and medical history and perform a physical exam. Often, these steps are enough to diagnose AN. Other tests to diagnose AN include:
Blood work, which can help confirm or rule out underlying conditions such as diabetes.
Skin biopsy (taking a sample of skin tissue), on rare occasions, if the diagnosis is not straightforward.
Will acanthosis nigricans go away on its own?
AN will not go away on its own, but you don’t always need medical treatment. If no underlying condition is causing AN, you can decide if you want to treat the dark patches.
Is acanthosis nigricans reversible?
People typically see good results after treatment. The skin clears, although the dark spots may not go away completely.
What treatments are available for acanthosis nigricans?
Treatment for AN depends on the cause. If AN is due to an underlying condition, such as diabetes or a hormonal condition, treating the condition will treat the skin problems.
Often, weight loss, exercise and a nutritious diet help reduce insulin levels, resulting in improved skin. The patches may even disappear completely.
Other treatments include:
Prescription creams to lighten the area.
Laser therapy or dermabrasion to reduce thickness.
Antibiotics to get rid of odor or discomfort.
Retinoids to help clear the skin.
Stopping certain medications that are causing AN.
Do not use skin care products to treat dark spots without consulting with a healthcare provider. These products may not work and may even irritate your skin, worsening the condition.
How can I manage acanthosis nigricans?
If the AN is related to elevated insulin, managing your weight and eating a healthy diet can help prevent or reduce the dark spots.
Can acanthosis nigricans be prevented?
If obesity is causing AN, you can help prevent the condition through weight management. A diet that helps you keep your blood sugar (insulin) levels in check can also help prevent AN.
Other preventive steps include:
Managing medical conditions related to AN, such as thyroid problems and diabetes.
Avoiding medications, such as birth control pills, that can cause or worsen AN.
What is the outlook for people with acanthosis nigricans?
AN isn't dangerous or harmful. People can live normal, healthy lives with AN.
However, it’s important to manage conditions that may be causing AN, such as diabetes, obesity or hormonal conditions. And if the dark patches appear suddenly, see your healthcare provider immediately. The sudden appearance may be a sign of cancer.
When should I see a dermatologist about acanthosis nigricans?
Any time you notice changes in your skin, see your healthcare provider or a dermatologist. Small markings or changes may seem insignificant, but they may indicate a problem. Acanthosis nigricans can be a sign of prediabetes or diabetes. Talk to your provider so you can get the proper care.
Acanthosis nigricans is a treatable skin condition that causes dark patches on your body. It is often (though not always) a sign of prediabetes or diabetes. Talk to your healthcare provider to find out if you have an underlying condition causing AN. A healthcare provider can help you get treatment to reduce the marks and help you feel and look your best.