Henoch-Schönlein purpura is an acute, systemic, immune complex-mediated, leukocytoclastic vasculitis. It is characterized by a triad of palpable purpura (without thrombocytopenia), abdominal pain, and arthritis. Most patients have an antecedent upper respiratory illness. More than 90 percent of Henoch-Schönlein purpura cases occur in children younger than 10 years; however, adults with this condition are more likely to experience complications than children. All patients with Henoch-Schönlein purpura develop a purpuric rash, 75 percent develop arthritis, 60 to 65 percent develop abdominal pain, and 40 to 50 percent develop renal disease. Because Henoch-Schönlein purpura spontaneously resolves in 94 percent of children and 89 percent of adults, supportive treatment is the primary intervention. Oral prednisone at 1 to 2 mg per kg daily for two weeks has been used to treat abdominal and joint symptoms. A meta-analysis found that corticosteroid use in children reduced the mean time to resolution of abdominal pain and decreased the odds of developing persistent renal disease. Early aggressive therapy with high-dose steroids plus immunosuppressants is recommended for patients with severe renal involvement. Long-term prognosis depends on the severity of renal involvement. End-stage renal disease occurs in 1 to 5 percent of patients.