hSP is a form of blood vessel inflammation, a vasculitis that affects small arterial vessels in the skin (capillaries) and the kidneys. Hsp results in skin rash associated with joint inflammation (arthritis) and cramping pain in the abdomen. Hsp frequently follows a bacterial or viral infection of the throat or breathing passages and is an unusual reaction of the body's immune system to this infection. Hsp occurs most commonly in children. Hsp is generally a mild illness that resolves spontaneously, but sometimes it can cause serious problems in the kidneys and bowels. Treatment is directed toward the most significant area of involvement. Joint pain can be relieved by antiinflammatory medications, such as aspirin or ibuprofen. Some patients can require cortisone-related medications, such as prednisone, especially those with significant abdominal pain or kidney disease. Also known as anaphylactoid purpura.