Acanthosis nigricans is visually identified as a pigmentation disorder, but it is not a disease, and so it is not actually classified as malignant, explains Healthline. In rare cases, the condition is caused by cancer, medications and other medical conditions. A doctor may order a biopsy to determine the cause.
High levels of insulin are the most common cause of the rapid skin cell reproduction that produces patches of acanthosis nigricans, notes Healthline. More uncommonly, it can also be caused by low levels of thyroid hormones, adrenal and pituitary gland disorders, stomach cancer, and high doses of niacin. Doctors most often check for diabetes or insulin resistance and review a patient's medications and supplements to find the cause. Once the underlying condition is known and addressed, the patches of discolored skin usually fade away.
Acanthosis nigricans affects ethnic groups with darker skin more than light-skinned groups because more melanin is produced in the new skin cells, says Healthline. In overweight individuals, ethnicity is not a primary consideration. The areas of the body most often affected are the elbows, groin, neck and knees. Patches may also appear on the knuckles, palms, lips and soles of the feet. Cosmetic treatments such as salicylic acid, Retin-A, alpha hydroxy acids and 20 percent urea can be used to cover the discolored skin, but these do not treat the underlying cause.