This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, Subject name: Pathology
[{'content': 'Frequency of renal involvement in HSP - \nSelect and explain. \nA. 20-40%, B. >80%, C. 40-60%, D. 10%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Henoch-Schonlein purpura(HSP) is an acute, systemic, immune complex-mediated, leukocytoclastic vasculitis. It is characterized by a triad of palpable purpura (without thrombocytopenia), abdominal pain, and ahritis. Most patients have an antecedent upper respiratory illness. More than 90 percent of Henoch-Schonlein 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-Schonlein purpura develop a purpuric rash, 75 percent develop ahritis, 60 to 65 percent develop abdominal pain, and 40 to 50 percent develop renal disease. www.aafp.org', 'role': 'assistant'}]