Anti-Bacterial Agents--therapeutic use Anti-Inflammatory Agents--therapeutic use Antistreptolysin--blood Autoantibodies--analysis Biopsy Child Child, Preschool Complement System Proteins--deficiency Dipyridamole--therapeutic use Female Humans IgA Vasculitis--complications Immunoglobulin A--analysis Immunoglobulin M--analysis Immunosuppressive Agents--therapeutic use Kidney--pathology Male Methylprednisolone--therapeutic use Platelet Aggregation Inhibitors--therapeutic use Prednisone--therapeutic use Proteinuria--drug therapy Retrospective Studies