3. Velvety, Brownish-Gray Patches of Skin
It could mean diabetes. Called acanthosis nigricans, this kind of discoloration commonly appears in creases and folds around the groin, underarms, and the neck; it can be an early warning sign for type 2 diabetes—a disease that can involve elevated levels of the hormone insulin. Excess insulin circulating in the blood may trigger abnormal growth in skin cells.
Dermatologists can sometimes diagnose acanthosis nigricans just by looking at your skin. The next step would be to see an internist for a diabetes test. If the result is positive, your doctor can recommend lifestyle changes and medication to manage the disease.