What Is Acanthosis Nigricans?

Acanthosis nigricans (AN) is a skin condition that is often a manifestation of another medical condition, although it can also occur by itself. Some medications can cause AN, as can genetics.

AN is a darkening and thickening of areas of the skin that is more common in people with dark skin pigmentation. There is treatment available, but treatment isn’t always necessary.

This article will discuss the types of acanthosis nigricans, symptoms, diagnosis, and treatment.

Types of Acanthosis Nigricans

Variations of acanthosis nigricans have been observed. One of these, called pseudoacanthosis nigricans, is associated with obesity. It is reversible and involves small areas of affected skin. These typically occur in body folds like between the buttocks, the groin, and under the arms.

Certain medications can also cause AN. These medications include human growth hormone and oral contraceptives.

A type of AN called malignant acanthosis nigricans occurs along with a cancerous tumor. It’s more common in adults, especially those over age 40. The underlying cancer is often adenocarcinoma of the stomach and, less commonly, adenocarcinoma of the ovary, uterus, pancreas, lung, or intestines. Sometimes it can occur with lymphoma.

Skin changes in malignant AN are usually more severe and sudden than with nonmalignant AN, including skin roughness and dryness, severe itching, and more significant pigmentation changes. Other symptoms of malignant AN include:

• Wartlike thickening around eyes
• Ridging or brittle nails
• Hair loss
• Thickening of the skin on the palms
  

Acanthosis Nigricans Symptoms

The main characteristics of AN is increased coloration (hyperpigmentation) and abnormal thickening of the skin. Areas often affected include the sides/back of the neck, arms, groin, and anal or genital areas. Sometimes it may be seen in skinfolds, like behind the knees, under the breasts, or the crooks of the elbows.

Symptoms of AN can include:

• Brown or black discoloration
• Skin that feels thicker and velvety
• Skin tags (a small growth attached to the skin surface by a base or stalk)
• Itching
• Bad odor

The symptoms often take time to develop—months or even years. It usually occurs in childhood or adolescence, getting worse during the teen years, but eventually improving.

Causes

 
Although there are a variety of condition-related causes of AN, it can also occur in healthy people. In the United States, it is most commonly found in people of African American descent.

Acanthosis nigricans can also be inherited as an autosomal dominant trait. This means only one parent has to have the gene for their offspring to have the condition, and it occurs equally in people of any sex.

Medically related causes of AN can include:

• Diabetes
• Obesity (which can also increase the risk of diabetes)
• Drugs like human growth hormone and oral contraceptives
• Lymphoma
• Cancers of the gastrointestinal tract or genitourinary tract

Diagnosis

A dermatologist (a physician specializing in skin conditions) can often diagnose AN by examining your skin and getting a complete medical history and family history.

Sometimes tests may be ordered like blood or urine tests. This is because AN is more common in those with diabetes, and it can also be a symptom of other ailments like prediabetes or thyroid conditions. These tests can help uncover these conditions so you may begin treatment to address them.

Tests may also be done to rule out autoimmune diseases. A biopsy (a sample of skin is removed to be analyzed in the laboratory) may be done to rule out cancer.

Treatment

Nonmalignant AN does not always need to be treated. If it bothers you, however, your dermatologist can provide treatment for AN aimed at relieving your symptoms.

If it’s caused by an underlying medical condition, treating that condition (like diabetes or insulin resistance) often improves skin issues with AN. Treatment can include dietary changes, changes in medication, and disease management.

In some people, skin symptoms do not improve, even after treating the medical condition.

Treatment can include:

• Lightening the skin: Prescription creams and ointment
• Reducing skin thickness: Laser treatments
• Reducing odor and itching or discomfort: Antibiotics, prescription soaps
• Taking steps to help clear the skin: Prescription retinoids

An oncologist (cancer specialist) is needed to treat people who have malignant AN. Treatment may include surgery, radiation, chemotherapy, or other anticancer treatments.

If AN is genetic, genetic counseling may be recommended.

Coping

If you’re self-conscious about your skin because of AN, see your primary care provider or a dermatologist. There are treatments that you can try to see if they reduce the appearance of the AN.

If you’re dealing with an underlying medical condition that is causing the AN, talk with your healthcare provider about how you’re feeling. They may know of a support group or counselor that can help you work through what’s going on.

Summary

Acanthosis nigricans is a common skin condition that may be a symptom of an underlying health condition like diabetes, insulin resistance, or even cancer. Treating the underlying health conditions can often reduce AN symptoms.

AN can also be treated with prescription creams or ointments, medications, laser treatments, antibiotics, and prescription soaps. Depending on your individual symptoms, treatment can vary.

A Word From Verywell

AN is treatable and manageable, but treatment isn’t always necessary. Talk with your healthcare provider about your symptoms, and if there are any other health conditions that may be causing your AN. Even if you don’t plan to treat your skin symptoms, it’s important to address the underlying health issues causing it.