Acanthosis nigricans is a skin condition characterized by the thickening and darkening of the skin, typically in the folds of the neck, armpits, and groin. It is often associated with obesity, insulin resistance, and diabetes. Synonyms for acanthosis nigricans include hyperkeratosis, hyperpigmentation, keratosis nigricans, and velvety dermatosis. Other medical conditions that may produce similar symptoms include Addison's disease, hypothyroidism, and certain medications. Treatment options for acanthosis nigricans may include weight loss and blood sugar management, as well as topical or oral medications to manage symptoms. It is important to consult with a healthcare provider for proper diagnosis and treatment.