C3 and Arthritis: In conclusion, our study highlights the following as factors associated with renal involvement in pediatric HSP: male gender, age > 10 years, severe gastrointestinal symptoms (including abdominal pain, gastrointestinal bleeding, and severe bowel angina), arthritis/arthralgia, persistent purpura or relapse, WBC > 15 × 109/L, platelets > 500 × 109/L, elevated ASO, and decreased C3.