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Acanthosis nigricans

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Acanthosis nigricans: Overview

What is acanthosis nigricans?

Acanthosis nigricans (ay-can-THOE-sis NIE-gri-cans) (AN) is a skin condition that causes one or more areas of skin to darken and thicken. The affected skin often feels velvety.

People who get this skin condition sometimes mistakenly believe that a dye or something else they touched has discolored their skin. Vigorous scrubbing will not get rid of the darkened skin.

Acanthosis nigricans is not contagious. It is not harmful. Sometimes, it is a warning sign of a health problem that requires medical attention. For this reason, it is important to see a dermatologist if you notice an area of darker, thicker skin.

When to see a dermatologist

If you notice a change to your skin, you should see a dermatologist. Small changes may seem like nothing. Sometimes a small change is an early warning sign. AN can be a sign of pre-diabetes, which increases your risk of getting diabetes. Making lifestyle changes before diabetes develops can prevent diabetes.

Some people get AN from a medicine that they are taking. Changing medicines might be an option for you. Other times, these dark patches have no connection to any medical condition. A dermatologist can help you find out what’s causing your skin changes.

Acanthosis nigricans: Signs and symptoms

This skin condition causes some easily recognized signs and symptoms. You may notice:

  • Brown or black discoloration on your skin.
  • Affected skin may feel velvety and thicker than the surrounding skin.
  • Skin tags may form on the darkened skin.
  • Skin can itch.
  • Skin can have a bad odor.

Where acanthosis nigricans forms

A velvety, dark patch of skin can form on most areas on the body, including the:

  • Armpits.
  • Back of the neck.
  • Groin area (especially in skin folds and creases).
  • Elbows. 
  • Knees.
  • Knuckles.
  • Belly button.
  • Woman’s breasts (beneath).
  • Face.
  • Female genitalia.

Less often, a patch can form on the lips, mouth, eyelids, palms of the hands, bottoms of the feet, and nipples.

Acanthosis nigricans (AN) tends to appear slowly, taking months or years to form. If it appears suddenly, you should immediately make an appointment to see a dermatologist. When AN appears suddenly, it can be a warning sign of cancer.

Acanthosis nigricans: Who gets and causes

Who gets acanthosis nigricans?

Anyone can get this skin condition. Some people, however, have a greater risk. People who are most likely to get acanthosis nigricans (AN) are:

  • Obese or overweight.
  • Of Native American, African, Caribbean, or Hispanic descent.
  • From a family with a history of AN.

What causes acanthosis nigricans?

People get this skin condition for many reasons. Obesity is the most common cause. Studies show that when obese children and adults who have AN lose a significant amount of weight, they often see their skin clear.

People who are completely healthy also get AN. These people tend to have others in their family with this skin condition. 

Sometimes, AN is a warning sign of something going on inside the body. It can warn about:

  • Pre-diabetes or diabetes: If you have pre-diabetes, making some lifestyle changes can help prevent diabetes. If you have diabetes, it is important to find out so that you can treat it.
  • A reaction to a medicine: Birth control pills, strong corticosteroids like prednisone, and niacin can cause AN.
  • Hormonal disease: This skin condition can be a sign of polycystic ovarian syndrome (PCOS), thyroid disease, or a problem with the adrenal glands.
  • Cancer: When AN develops quickly, it can be a sign of a cancer, especially a cancer in the stomach, colon, or liver.

Acanthosis nigricans: Diagnosis and treatment

How do dermatologists diagnose acanthosis nigricans?

A dermatologist can diagnose acanthosis nigricans (AN) by looking at your skin. If your dermatologist diagnoses you with AN, you may need a blood test and other medical tests. These tests can help find out if you have another medical condition. AN is more common in people who have diabetes. Sometimes, AN can be a warning sign of pre-diabetes, thyroid disease, and other conditions.

How do dermatologists treat acanthosis nigricans?

Many people see their skin clear when they get treatment for the condition that is causing AN. If you have pre-diabetes, getting that under control often helps to fade the dark patches on your skin. If testing finds a problem with your thyroid or adrenal glands, treating that condition can clear your skin.

Sometimes, a person develops AN but does not have a related medical condition. Sometimes treating the related disease does not completely clear the skin. It is not necessary to treat AN. If a patient wants clearer skin, a dermatologist can treat the skin.

Treatment for AN includes the following:

  • Lighten skin color: Prescription creams, ointments, and gels.
  • Reduce skin thickness: Laser treatments.
  • Decrease odor and discomfort: Antibiotics you apply to the skin and antibacterial soaps.
  • Help clear the skin: Retinoids (in pill form).

None of these treatments is specifically designed to treat AN. Dermatologists have found, however, that these can help. Sometimes, AN is difficult to treat. 

Outcome

If you have AN, it is essential to find out whether another disease is causing it. Finding and treating an undiagnosed disease may clear (or partially clear) your skin. If a disease is not causing your AN or you do not see the results you want from treating a related disease, a dermatologist can treat your skin.

Studies show that many obese people see the dark patches on their skin clear when they lose a significant amount of weight.

Acanthosis nigricans: Tips for managing

Dermatologists offer these tips to their patients who have acanthosis nigricans (AN):

  • Maintain a healthy weight. Obesity is the most common cause of AN in adults and children. Studies have found that people’s skin often clears completely with significant weight loss. You can find out what your healthy weight is by calculating your body mass index.
  • Before using a bleaching cream, exfoliant, or other skin care product, ask a dermatologist if you should use it. These products rarely fade AN and can irritate your skin, making AN worse.
  • Find out if you have a medical condition that is causing AN. Diabetes and other medical conditions can cause AN. Doing things that improve the medical condition often help to clear the skin.
  • Find out if a medicine you take is causing AN. Some medicines can cause AN. Be sure to tell your dermatologist about all the medicines you take. If medicine is causing your AN, you may be able to switch to another medicine.
  • If you suddenly see many dark, velvety patches on your skin, immediately make an appointment to see your dermatologist or primary care doctor. This can be a sign of cancer.

More resources:

  1. Why is a healthy weight important?
  2. National Diabetes Information Clearinghouse
  3. Polycystic Ovarian Syndrome Foundation

References:

Habif TP, Campbell JL, Chapman MS, et al. “Acanthosis nigricans.” Dermatology DDxDeck. Mosby. 2006.

Hermanns-Le T, Scheen A, Pierard GE. “Acanthosis Nigricans Associated with Insulin Resistance.” Am J Clin Derm. 2004;5(3):199-203.

Kapoor S. “Diagnosis and treatment of acanthosis nigricans.” Skinmed. 2010 May-Jun;8(3):161-4; quiz 165.

Sinha S, Schwartz RA. “Juvenile acanthosis nigricans.” J Am Acad Dermatol. 2007;57:502-8.

Yosipovitch G, DeVore A, Dawn A. “Obesity and the skin: Skin physiology and skin manifestations of obesity.” J Am Acad Dermatol. 2007;56:901-16.

Sinha S, Schwartz RA. “Juvenile acanthosis nigricans.” J Am Acad Dermatol. 2007;57:502-8.

Weger W, Ginter-Hanselmayer G, et al. “Florid cutaneous papillomatosis with acanthosis nigricans in a patient with carcinomas of the lung and prostate.” J Am Acad Dermatol. 2007;57:907-8.

Yosipovitch G, DeVore A, and Dawn A. “Obesity and the skin: Skin physiology and skin manifestations of obesity.” J Am Acad Dermatol. 2007; 56:901-16.

American Diabetes Association, “Type 2 diabetes,” available at http://web.diabetes.org/wizdom/download/type2.asp. Last accessed September 2012.

Kapoor S. “Diagnosis and treatment of acanthosis nigricans.” 2010 May-Jun;8(3):161-4; quiz 165.

Sinha S, Schwartz RA. “Juvenile acanthosis nigricans.” J Am Acad Dermatol. 2007;57:502-8.

Stuart CA, Gilkison CR, Smith MM, et al. Acanthosis nigricans as a risk factor for non-insulin dependent diabetes mellitus. Clin Pediatr 1998;37:73-9.

Yosipovitch G, DeVore A, Dawn A. “Obesity and the skin: Skin physiology and skin manifestations of obesity.” J Am Acad Dermatol. 2007;56:901-16.

Hermanns-Le T, Scheen A, Pierard GE. “Acanthosis Nigricans Associated with Insulin Resistance.” Am J Clin Derm. 2004;5(3):199-203.

Kapoor S. “Diagnosis and treatment of acanthosis nigricans.” Skinmed. 2010 May-Jun;8(3):161-4; quiz 165.

Sinha S, Schwartz RA. “Juvenile acanthosis nigricans.” J Am Acad Dermatol. 2007;57:502-8.

Yosipovitch G, DeVore A, Dawn A. “Obesity and the skin: Skin physiology and skin manifestations of obesity.” J Am Acad Dermatol. 2007;56:901-16.

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