Not unusual.Often skin in the genital area is darker especially in certain persons of color. Most commonly in the crural (crease) and or on the labia in women. It also darkens in some due to friction eg bike riders. Don't forget to rule out "jock itch"Scrotum is usually unaffected.

You need to be seen by the dermatologist. It can be a fungal infection or some other type of infection.

Suzanne Sirota Rozenberg, DO, FAOCD