Understanding Acanthosis Nigricans (AN)

Acanthosis nigricans (AN) is a skin condition characterized by darkened, thickened, and often velvety patches of skin. These changes typically occur on the back of the neck, elbows, knees, ankles, and other body folds. The "rash" is usually symmetrical, appearing on both sides of the body, and may be accompanied by numerous skin tags. The affected skin may feel soft or velvety to the touch and can occasionally be itchy.

Close-up of acanthosis nigricans present on the neck. At the bottom left of the image, many skin tags are present. Note that the skin appears dirty.

AN Associated with Insulin Resistance and Obesity

The most common cause of AN is insulin resistance, regardless of the underlying reason. Elevated levels of insulin and insulin-like growth factor (IGF), both of which are growth-promoting hormones, appear to drive the skin changes seen in AN. Even the use of injectable (exogenous) insulin—such as in individuals with Type 1 Diabetes Mellitus—can contribute to the development of this condition.

Friction and perspiration, especially in skin folds, may further exacerbate the condition.

Childhood and adolescent obesity are particularly significant risk factors for AN and often indicate underlying insulin resistance.

AN Related to Malignancy

In rare cases, AN can be associated with internal malignancies, a condition referred to as malignant acanthosis nigricans. While uncommon, malignant AN is a potential sign of an underlying cancer. The condition is not cancer itself but is thought to be triggered by growth factors secreted by tumor cells, such as transforming growth factor-alpha (TGF-α).

Malignant AN typically occurs in older individuals and presents more suddenly and severely than other forms. It may appear before, during, or after a cancer diagnosis.

AN Due to Autoimmune Disease

Acanthosis nigricans may also occur in association with autoimmune conditions, particularly:

• Hashimoto's thyroiditis (most common)

• Systemic lupus erythematosus (SLE)

• Scleroderma

Hashimoto's thyroiditis, an autoimmune condition that leads to hypothyroidism, is most frequently associated with AN among these.

AN Due to Rare Genetic Conditions

There are over 25 rare genetic disorders and syndromes linked to the development of AN. These are uncommon but should be considered, particularly when AN presents early in life or alongside other congenital abnormalities.

Can Acanthosis Nigricans Be Cured?

Unfortunately, AN is difficult to cure completely. There is no universally accepted treatment. Topical therapies, chemical peels, and laser treatments are primarily cosmetic and may not prevent recurrence.

The most effective strategy is addressing the underlying cause. In cases of insulin resistance, improving insulin sensitivity through lifestyle changes, medications, or weight loss is essential. Reversing insulin resistance lowers insulin and IGF levels. In individuals with obesity, reducing excess body fat can help, as enlarged fat cells contribute to hormonal imbalances that drive the skin changes. When it comes to acanthosis nigricans, prevention is truly worth more than cure.