Picture of Acanthosis Nigricans
Acanthosis nigricans is a condition that results in the appearance of dark, thickened patches of skin that feel velvety. The affected skin most often appears in areas where there are skin folds, including the groin, armpits, knees, elbows, and the back of the neck. Many different conditions may trigger acanthosis nigricans including diabetes, cancer, polycystic ovary syndrome (PCOS), thyroid disease, and adrenal gland disorders. Certain medications, including corticosteroids and birth control pills, may trigger acanthosis nigricans.
Text Reference: American Academy of Dermatology: "Acanthosis Nigricans"