What Is Acanthosis Nigricans?
Acanthosis nigricans is a fairly common skin pigmentation
disorder. The most notable sign of acanthosis nigricans is dark patches of skin
with a thick, velvety texture.
These patches may appear on skin folds and the:
- soles of the feet
Acanthosis nigricans may be a sign of a more serious health
problem, such as prediabetes. The most effective treatments focus on finding
and resolving medical conditions at the root of the problem. These skin patches
tend to disappear after successfully treating the root condition.
Pictures of Acanthosis Nigricans
Who Is at Risk for Acanthosis Nigricans?
Acanthosis nigricans is seen in both men and women. It’s most
common in those who are overweight, have darker skin, and have diabetes or prediabetic
The frequency of acanthosis nigricans varies between ethnic
groups. One study found that acanthosis nigricans appears in 34 percent of Native
Americans. According to the American
Academy of Dermatology, people of African, Caribbean, or Hispanic descent
are also at an increased risk. All ethnic groups are equally at risk of
acanthosis nigricans when body mass index (BMI) is well above normal.
What Causes Acanthosis Nigricans?
Acanthosis nigricans skin patches occur when epidermal skin cells
begin to reproduce rapidly. This abnormal skin cell growth is most commonly
triggered by high levels of insulin in the blood. In rare cases, the increase
in skin cells may be caused by medications, cancer, or other medical
Too Much Insulin
The most frequent trigger for acanthosis nigricans is too much
insulin in your bloodstream.
When you eat, your body converts carbohydrates into sugar
molecules such as glucose. Some of this glucose is used for energy in your
cells while the rest is stored. The hormone insulin must allow glucose to enter
cells so that the cells can use glucose for energy.
Overweight people tend to develop resistance to insulin over
time. Although the pancreas is making insulin, the body can’t use it properly.
This creates a buildup of glucose in the bloodstream, which can result in high
levels of both blood glucose and insulin
in your bloodstream.
Excess insulin causes normal skin cells to reproduce at a rapid
rate. For those with dark skin, these new cells have more melanin. This
increase in melanin produces a patch of skin that’s darker than the skin
surrounding it. Thus, the presence of acanthosis nigricans is a strong
predictor of future diabetes. If too much insulin is indeed the cause, it’s
relatively easy to correct with proper diet, exercise, and blood sugar control.
Acanthosis nigricans can also be triggered by certain medications
such as birth control pills, human growth hormones, thyroid medications, and
even some bodybuilding supplements. All of these medications can cause changes
in insulin levels. Medications used to ease the side effects of chemotherapy
have also been linked to acanthosis nigricans. In most cases, the condition
clears up when the medications are discontinued.
Other Potential Causes
In rare cases, acanthosis nigricans can be caused by:
- stomach cancer, or gastric adenocarcinoma
- adrenal gland disorders, such as Addison’s
- disorders of the pituitary gland
- low levels of thyroid hormones
- high doses of niacin
How Is Acanthosis Nigricans Diagnosed?
Acanthosis nigricans is easy to recognize by sight. Your doctor
may want to check for diabetes or insulin resistance as the cause. These tests
may include blood glucose tests or fasting insulin tests. Your doctor may also
review your medications to see if they’re a contributing factor.
It’s important to tell your doctor about any dietary supplements,
vitamins, or bodybuilding supplements you may be taking in addition to your
In rare cases, your doctor may perform other tests, such as a
small skin biopsy, to rule out other possible causes.
How Is Acanthosis Nigricans Treated?
Acanthosis nigricans isn’t a disease. It’s a symptom of another
condition that may require medical attention. Treatment is largely focused on
addressing the condition that’s causing it. If you’re overweight, your doctor
will advise you to lose weight. Your doctor may also prescribe medications to
help bring your blood glucose under control.
If the condition is caused by medications or supplements, your
doctor may have you discontinue them or suggest substitutes. The discolored
skin patches will usually fade when you find the cause and get it under
Cosmetic treatments exist for cases that are especially unsightly
or embarrassing. Dark patches may be covered up with cosmetics or lightened
with prescription skin lighteners. Although these treatments aren’t as
effective as treating the cause of the condition, they can provide some relief.
Available skin lighteners include Retin-A, 20 percent urea, alpha hydroxy
acids, and salicylic acid.
Ongoing Care and Prevention
Maintaining a healthy lifestyle can usually prevent acanthosis
nigricans. Losing weight, controlling your diet, and adjusting any medications
that are contributing to the condition are all crucial steps. Healthier
lifestyle choices will also reduce your risks for many other types of