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Definition  

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.

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Causes  

Causes of acanthosis nigricans may include:

  • High insulin levels in people who are obese
  • A family history of acanthosis nigricans
  • A cancerous tumor (rarely)
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Risk Factors  

Risk factors that increases your chance of getting acanthosis nigricans include:

  • Being overweight
  • Type 2 diabetes
  • Polycystic ovary syndrome (PCOS)
  • Heredity: People of African-American descent are more likely to develop acanthosis nigricans
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Symptoms  

If you experience any of these symptoms, do not assume it is due to acanthosis nigricans. These symptoms may be caused by other health conditions.

  • Velvety-looking, dark areas on:
    • Back of the neck
    • Armpits
    • Groin
    • Elbow
    • Knees
    • Knuckles
    • Face
    • Palms
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Endoscopy  
Endoscope in stomach

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Diagnosis  

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
  • Imaging tests such as X-rays or endoscopy to rule out other causes
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Treatment  

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.

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Prevention  

The best way to reduce your chances of getting acanthosis nigricans is to maintain a healthy weight through diet and regular exercise.