Acanthosis nigricans refers to a pigmentation disorder characterized by brown to black, thickened, velvety patches in different parts of the body.
It is most commonly seen in the neck, armpit, and groin. It may also be seen in knees, elbows, knuckles, palms and soles of feet.
This skin condition is not a disease in itself, but a symptom of an underlying medical condition like diabetes and obesity. In some cases, it is seen associated with cancer of internal organs like liver and stomach.
Treating the underlying medical conditions helps to control pigmentation and to restore normal skin conditions. It is found more commonly among Africans, Caribbean and Hispanics.
Darkening and thickening of the skin, particularly in the neck, armpit, and groin are the major symptoms of Acanthosis Nigricans. Skin changes appear gradually over a period of time, and may also be associated with itching.
Changes occur abruptly, if the condition is associated with cancer. The patches are usually dry and velvety in appearance. In some cases, skin tags may be found near the affected area.
The dry patches may also have small finger-like projections, known as papillomatosis, on the surface. If the skin discoloration occurs suddenly, it is better to consult a physician.
The main causes of Acanthosis nigricans are:
Insulin resistance – high levels of insulin in the blood trigger rapid proliferation of skin cells. The new cells thus formed have more amounts of pigment melanin which make the patch darker than the surrounding skin.
Obesity – this is one of the most common form of acanthosis. The patches are mostly found in adults, but may develop at any age. The patches regress once the person loses weight successfully.
Syndromes – Acanthosis nigricans is associated with a number of syndromes like acromegaly, Barter syndrome, gigantism, bloom syndrome, and phenylketonuria.
Certain medications – medications like nicotinic acid, pituitary extract, and systemic corticosteroids are known to trigger patch formation. Discontinuation of the medicine helps to resolve the condition.
Hormonal disorder – disorders of endocrine glands also lead to acanthosis.
Cancer – pigmentation due to internal malignancy is one of the most worrisome form of acanthosis.
In some cases, this skin condition is inherited. The patches may start forming from early childhood, and often regresses by the 14-15 years of age.
4 Making a Diagnosis
Making a diagnosis of Acanthosis nigricans is done by physical examination.
The only specific treatment towards Acanthosis nigricans is cosmetic correction of the dry patches.
Treating the underlying disease helps to regress pigmentation. The doctor may suggest to correct diabetes through medication and diet. If the skin condition is associated with obesity, losing weight is the solution.
If a certain medication is the cause of pigmentation, stopping the medication resolves acanthosis. A hereditary form of acanthosis may develop gradually and usually regress on its own.
Acanthosis caused by cancer is resolved by treatment of the tumor. To improve the appearance of the affected skin, a number of cosmetic procedures are available:
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