Acanthosis nigricans

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at April 21, 2016
StartDiseasesAcanthosis nigricans

Acanthosis nigricans is a skin condition that appears as a dark, patchy or velvety discoloration. Occurring mostly on skin folds on the elbows, armpits, knees, neck, or groin, it is often caused by genetic factors or hereditary factors. Sometimes it occurs in those who are obese or who have certain existing conditions such as insulin resistance or Cushing's syndrome.


Definition & Facts

Skin discolorations have many causes, but acanthosis nigricans is defined by a darkened patch of skin that becomes thicker and more velvety in texture. The hyperpigmentation often starts out very small but may spread to cover an area of several square inches or more. This type of hyperpigmentation is not associated with sun exposure or other environmental factors. The darkened area affects skin folds because these areas have skin cells with slightly different structure.

It generally affects younger individuals and is rarely seen as a developing condition in adults over the age of 40. Children often show signs of acanthosis nigricans as a precursor to the symptoms of diabetes. Young children who show this discoloration symptom are at a significantly higher risk of developing type 2 diabetes.

Symptoms & Complaints

Changes in skin color can signal any number of medical conditions. However, acanthosis nigricans has no other outward signs except the patchy, poorly defined darkening around skin folds. People often don't notice the color change immediately because it comes on quite gradually. Usually, a small area begins to darken, the wrinkles become more noticeable in the affected area, and the skin texture becomes softer.

The discoloration may start out as a dark red blotch, similar to a bruise or rash. Eventually, the area becomes grayer and the patch begins to spread. Most people with symptoms of this kind of hyperpigmentation begin to exhibit one or more areas where the skin seems to contain a large amount of melanin.

The most common complaint by individuals who seek medical attention is that the skin in the affected region has a softer feel and that the skin layers appear to have thickened. In most cases, the discoloration stops spreading after a short period of time, but some individuals notice a second and even a third patch beginning to appear in another area of the body where the skin is folded.


Acanthosis nigricans has been positively linked to other medical conditions. The most common are hormonal disorders, resistance to insulin, and cancer. Insulin resistance is the cause of type 2 diabetes, a disease that affects countless millions of people worldwide. Some people have been diagnosed with reactions to certain drugs and food supplements, with dark patch formation on the skin as a side effect.

An ovarian cyst, hypothyroidism, or adrenal gland malfunction can also cause this dark pigmentation. When a tumor starts to grow in an internal organ or if the individual has lymphoma, darkly colored skin can begin to appear. In this case, the pigmentation changes is a direct result of the cancerous growth and how the tumor is affecting the rest of the body.

Diagnosis & Tests

The doctor will ask about the patient's medical history. Sometimes an individual doesn't notice a small area of dark skin until it shows up during a routine physical examination. At first, the doctor will not be able to clearly define the problem as acanthosis nigricans. Blood tests may be ordered up and a biopsy performed. The concern for the doctor is whether a darkened skin patch is a sign of possible tumor growth somewhere in the body.

If a well-developed yet poorly defined darkened area has been detected, the doctor may want to perform X-rays to try and locate a malignant growth. The tumor, if it exists, may be located far from the darkened skin patch. It is therefore necessary to combine several tests to determine the most likely cause. Additional tests may include endoscopy and colonoscopy.

Treatment & Therapy

Treatment options vary and are dependent on the underlying cause of the pigmentation. If diabetes and cancer have been ruled out, further examination may determine that the skin pigmentation is due to obesity, the taking of certain drugs or food supplements, or other factors such as genetics. Changing the diet, losing weight, and abstaining from certain medications may be advised. If the problem is linked to cancer, surgically removing the tumor - if that is possible - may result in a clearing up of the skin discoloration.

In most cases, skin conditioning substances will not be effective because the skin cells themselves have been altered. Skin resurfacing techniques such as abrasion and chemical peels are likewise ineffective. However, individuals will be advised by their doctor or a dermatologist about how to best reduce the appearance of the darkened areas. Certain creams, lotions, and prescription ointments may help to lighten the skin. Laser therapy may also help to lighten the skin and reduce the outward signs of acanthosis nigricans. Laser therapy can be used to thin out the skin layers and make the area appear lighter.

Prevention & Prophylaxis

Since acanthosis nigricans is sometimes caused by the taking of certain drugs, it is highly recommended that individuals talk to their doctor about possible adverse reactions and side effects when any drug is prescribed.

Parents who have experienced this condition should talk to their doctor if the mother is pregnant. This can help the pediatrician make recommendations about how to spot possible health problems in the newborn child. Otherwise, the best advice for children, teens, and young adults is to eat a healthy diet, maintain a healthy weight, and to avoid dangerous drugs.