Keratosis Nigricans is a skin condition characterized by dark, thick, and velvety patches on the skin. This condition usually occurs in areas such as the neck, armpits, and groin. Some synonyms for Keratosis Nigricans include Acanthosis Nigricans, AN, Pigmented Acanthosis, Benign Papillomatosis, and Unguis Incarnatus. These synonyms are used interchangeably to describe the condition and its symptoms. Keratosis Nigricans is usually associated with obesity, insulin resistance, and high levels of insulin in the blood. While it's not a harmful skin condition, it's essential to seek medical attention if you notice any changes in your skin texture or color.