Acanthosis nigricans

What is acanthosis nigricans?

Acanthosis nigricans (sometimes shortened to AN) is a condition that makes patches of your skin thicker and darker. It’s usually a sign of another underlying condition , so it’s recommended you seek help to get your symptoms under control as soon as they start to develop (as well as find out what might be causing it).^[1]

Although the usual affected areas are your neck, armpits and groin, dark patches can form on other parts of your body, including:

• in your creases and folds of skin;
• the elbows;
• the knuckles;
• the face;
• the lips;
• the back of your neck;
• the soles of your feet; and:
• the palms.

Women can sometimes develop the patches underneath their breasts. A clinician can give you specific advice if you develop acanthosis nigricans in any unexpected areas or parts of your body not listed above.

As well as becoming darker, the texture of affected skin can also change, becoming thicker and ‘velvety’. Sometimes, you might also see papillomatous overgrowths of the epidermis (your top layer of skin). Papillomatous growths (papillomas) are usually benign.

If your symptoms indicate acanthosis nigricans is causing your skin problems, a clinician will usually advise you to have some tests done. These can be carried out by your GP, and can help establish the root cause of your condition.

Who gets acanthosis nigricans?

Anyone can develop acanthosis nigricans, but it typically affects people under the age of 40.

Those most at risk of getting it are people who are:

• overweight;
• from African, Native American, Hispanic or Caribbean descent; or:
• from a family that has a history of acanthosis nigricans.

Although the exact cause of acanthosis nigricans is unclear, it commonly affects people with diabetes and insulin resistance.^[2]

How common is acanthosis nigricans?

While it’s hard to say exactly how common acanthosis nigricans is, there is some evidence that suggests people with black or brown skin are more likely to be affected by it.^[3]

Sometimes, symptoms develop in otherwise healthy people for no apparent reason. Often, though, acanthosis nigricans is caused by another condition, such as type 2 diabetes.

An HbA1c (glycated haemoglobin) test can determine whether you have too much sugar in your blood. If diabetes or any other condition is behind your acanthosis nigricans, your GP can advise you about the best treatments and management plans available. Our clinicians are also on hand to answer questions about suitable options that can help you.

What causes acanthosis nigricans?

There isn’t always a cause for acanthosis nigricans, but more often than not there are underlying reasons why darkened, thick patches of skin have developed. Pre-existing conditions (you may or may not be aware of), medications, or treatments that affect your hormones can all contribute to the condition. These include:

• type 2 diabetes;
• an underactive thyroid, or conditions that change hormone balances like Cushing’s syndrome or polycystic ovary syndrome;
• specific medications, like steroids or the contraceptive pill (that affect your hormones);
• cancer (typically stomach cancer, although this is a rare cause); or:
• an inherited gene.

Pinpointing a cause for your acanthosis nigricans is usually the first step for finding suitable treatment options.

What are the symptoms of acanthosis nigricans?

The most common symptom of acanthosis nigricans is the development of dry, dark patches of skin on your body. They can appear anywhere, but usually affect your armpits, neck, and groin.

The affected areas typically become thicker, and can have a velvet-like feel. They often occur in skin folds, and sometimes have skin tags (small growths of skin) attached to them. The skin on the affected areas can sometimes be itchy, or have an odour.

Can acanthosis nigricans lead to other problems?

While acanthosis nigricans might not lead to further health complications, darkened patches of thick, ‘velvety’ skin are often a sign of another condition, such as diabetes. For this reason, you’ll usually be asked to provide test results so our clinicians can make a thorough diagnosis before offering treatments.