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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)

