Hidradenitis suppurativa (HI-drad-en-I-tis sup-per-ah-TEE-vah or HS) is a chronic condition with recurrent painful bumps and draining sores of the skin. Sometimes it can look like acne. It more commonly affects the skin folds, such as the underarms, buttock crease, and groin area. When severe, it can appear in other parts of the body as well. HS seems to be more common in people with Down syndrome.
Source: The Society for Pediatric Dermatology