Acanthosis Nigricans & Hyperpigmentation

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Acanthosis nigricans is an area of pigmentation on the skin which is brown or black in colour. It is usually found in creases of the skin such as in the neck and groin. It occurs most often in people under the age of 40 and can be inherited from your parents.

How does insulin cause acanthosis nigricans?

Insulin resistance is what most commonly causes acanthosis nigricans. Increased amounts of insulin in the blood can cause tougher, thicker and darker areas of skin in the creases and these signs are suggestive of insulin resistance.   Type 2 diabetes is the most common condition linked with insulin resistance.

Medications which cause insulin levels to increase can also cause acanthosis nigricans. This includes steroids, insulin, oral contraceptives and some anti-viral medicines used to treat human immunodeficiency virus (HIV) and hepatitis C.

Is acanthosis nigricans linked with cancer?

Acanthosis nigricans can sometimes be caused by cancer. When this happens, it is usually called acanthosis nigricans maligna. When acanthosis nigricans is found in people over the age of 40 it is often caused by cancer. When it is found in the mouth or on the tongue then it is usually caused by cancer in the stomach.

Who gets acanthosis nigricans?

Acanthosis nigricans is a condition that is much more common if you have dark skin. In white people it is quite rare. It is thought to affect around one in ten African Americans. If you are a Native American and have diabetes then you will almost certainly have acanthosis nigricans. It is also much more likely that you will have acanthosis nigricans if you are overweight or obese.

Acanthosis nigricans which is linked to cancer can affect anybody.

How to diagnose acanthosis nigricans

Acanthosis nigricans can be easily diagnosed by a doctor just by looking at your skin. If it is not clear what is causing the acanthosis nigricans then it is usually necessary to find out what this is. This can be done by blood tests, endoscopy or x-rays in order to see if you have diabetes or cancer.

Acanthosis nigricans can look similar to symptoms found in a vitamin deficiency disease called pellagra, which can be easily treated. It can be hard to tell the difference between the two conditions so tests may be needed to do this.

How to treat acanthosis nigricans

The best way to treat acanthosis nigricans is to treat what is causing it, that is usually diabetes or cancer. Controlling blood glucose levels through both diet and exercise is usually an effective treatment. If the acanthosis nigricans is caused by cancer then removal of the tumour often cures it. If the acanthosis nigricans is caused by a drug then changing to a different medication will help.

There are some medicines which can be applied directly to the area which can help to reduce the appearance of acanthosis nigricans. This includes keratolytics that help cause peeling of the skin, and creams to reduce pigmentation. It is best to apply these medications along with sunscreen.

Some oral medicines such as etretinate, isotretinoin, metformin and dietary fish oils can be used to reduce its appearance but don’t remove the acanthosis nigricans.

Dermabrasion, which involves scraping away the skin, can be used to reduce the amount of acanthosis nigricans.

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