What is acanthosis nigricans?
Acanthosis nigricans is a type of skin condition characterized by thick dark (hyperpigmented) skin which tends to occur on the skin folds – armpits (axillae), neck, and groin. Typically the hyperpigmented skin has a velvety texture and can therefore be clearly differentiated from hyperpigented areas of normal skin. Acanthosis nigricans can occur with certain diseases and has gained much attention in recent years due to its association with obesity and insulin resistance as is seen in type 2 diabetes mellitus (sugar diabetes).
There are two types of acanthosis nigricans with several different catgeories. The same process is involved in all types and forms of acanthosis nigricans which involves rapid stimulation of the dermis and epidermis of the skin by most commonly by hormonal factors. This results in overgrowth (hyperplasia) and thickening (hyperkeratosis) of the skin with increased melanin deposition (hyperpigmentation) although the number and size of the melanocytes (pigment-producing skin cells) remains the same. The proliferation of the dermal papillae contributes to the velvet texture of the affected area. Acanthosis nigricans is a benign skin condition. Even when associated with malignancy, it is not due to cancer of the skin or at the site but a manifestation due to a tumor elsewhere in the body (paraneoplastic).