I would like to suggest a category, possibly under dermatology, for Hidradenitis
Suppurativa (also known as H.S.,, Verneuil's disease, etc). This is a skin disease that is painful an can be debilitating, affecting up to 4% of the population. It causes painful abscesses/cysts/boils in the underarm, breast, buttocks, and groin areas. It is often misdiagnosed and often goes undiagnosed for years (for example, I've had it for 14 years and was just formally diagnosed 2 years ago).