FOCUS QUESTIONS 1. What is our understanding of the pathophysiology of Henoch. Schoenlein purpura (HSP)? 2. What are the cardinal clinical features of HSP? 3. Which clinical features offer substantial threat to survival or full recovery from HSP? 4. What clinical or laboratory observations are required for or appropilate to monitoring the course of HSP? 5. What therapeutic measures are available for HSP, and what clinical features direct their choice and use?

The distinctive syndrome of Henoch-Schoenlein purpura (HSP) was first described by Heberden before 1800, and in 1808 English physician Robert Willan described a patient who had swollen, painful joints and a rash. The syndrome owes its name to two German physicians. In 1837, Johan Schoenlein described several cases of purpura associated with arthritis, which he termed "peliosis rheumatica." In 1868, Edouard Henoch pointed out that the term "peliosis rheumatica" was inappropriate and restrictive because patients who had urticarial purpura and acute arthritis also manifested gastrointestinal symptoms, such as vomiting, colicky abdominal pain, and melena. He described four children who had purpura, colicky abdominal pain, gastrointestinal hemorrhage, and joint pain as well as renal involvement.1 Since these first descriptions, HSP also has been referred to as anaphylactoid, allergic, or rheumatoid purpura; leukocytoclastic vasculitis; and allergic vasculitis.1,2 Epidemiology Seventy-five percent of all cases of HSP occur in children between 2 and 11 years of age, with younger children rarely affected. Children younger than 2 y experience a milder course of illness, with less frequent renal and gastrointestinal manifestations.3 HSP is exceedingly rare in adults, among whom other causes of vasculitis should be considered more likely. The incidence of HSP is greater in males, with a male-to-female ratio of 1.5 to 2.0:1.