Henoch-Schonlein purpura. Hemorrhagic macules, papules, and urticarial lesions on the foot of a child with Henoch-Schonlein purpura. Henoch-Schonlein purpura (HSP) is a form of blood vessel inflammation or vasculitis. HSP occurs most commonly in children, but people of all age groups can be affected.

Classically, HSP causes skin rash, pain in the abdomen, and joint inflammation (arthritis). The rash of skin lesions appears in gravity-dependent areas, such as the legs. The joints most frequently affected with pain and swelling are the ankles and the knees. The treatment of HSP is directed toward the most significant area of involvement. Joint pain can be relieved by antiinflammatory medications such as aspirin or ibuprofen (Motrin).