A form of blood vessel inflammation that affects small capillaries in the skin and the kidneys. It results in skin rash associ- ated with joint inflammation (arthritis) and cramp- ing pain in the abdomen. Anaphylactoid purpura frequently follows a bacterial or viral infection of the throat or breathing passages, and it is an unusual reaction of the body’s immune system to this infec- tion. It occurs most commonly in children. Generally a mild illness that resolves spontaneously, anaphylactoid purpura can sometimes cause serious problems in the kidneys and bowels. Treatment is directed toward the most significant area of involve- ment. Also known as Henoch-Schonlein purpura (HSP).