Acanthosis nigricans is a skin condition in which brown or black velvet-like markings appear under the arms, in the groin, or on the back of the neck. Any skin fold can be affected, including the lower lip and chin.

Causes of acanthosis nigricans may include:

• High insulin levels in people who are obese
• A family history of acanthosis nigricans
• Rarely, a cancerous tumor

Acanthosis nigricans is more common in people of African-American decent. Other factors that increase your chances of getting acanthosis nigricans include:

• Being overweight
• Type 2 diabetes
• Polycystic ovary syndrome

Symptoms include velvety-looking, dark areas anywhere on the skin.

Your doctor will ask about your symptoms and medical history. A physical exam will be done. Tests may include the following:

• Skin biopsy
• Blood tests
• X-rays
• Endoscopy

Endoscopy

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Treatment often involves treating the underlying cause. For example, if acanthosis nigricans is due to obesity, weight loss can improve the skin condition.

Topical and oral retinoids and other medicines have been reported to improve appearance in some cases. They help remove excess layers of skin.

To reduce your chances of getting acanthosis nigricans, take these steps:

• Maintain a healthy weight
• Eat a balanced diet
• Get regular exercise most days of the week
• Talk to your doctor about your blood sugar levels