A single-center study of C1q nephropathy in children.

C1q nephropathy (C1qN) is a rare idiopathic glomerulopathy typically seen in adolescents and young adults. All kidney biopsies done from 2002 to 2007 were analyzed (264). Thirteen cases of C1qN from 212 (6.6%) native biopsies and one case out of 52 (1.9%) transplant biopsies were reviewed regarding demographic features, clinical presentation, histopathology, treatment, and outcome. Age varied from 1 to 18 years; half were boys. Ten children (71.4%) presented with nephrotic syndrome (NS). The most common histopathology found was diffuse mesangial proliferative glomerulonephritis (DMP) by light microscopy (LM), with diffuse granular staining for C1q predominantly in the mesangium. Children with either NS or persistent gross hematuria received prednisone and angiotensin-converting enzyme inhibitors (ACEi) (11). Median follow-up was 36 months. Steroid response was complete in 6 patients (54.5%). Those with steroid resistance (5) or steroid dependence (2) received further immunosuppression with mycophenolate mofetil (MMF) or tacrolimus (Tac). Three children achieved complete remission and four partial remission. Frequent relapses were seen in 4/14 patients. Renal survival was 100%. Our report reveals a high incidence of C1qN in pediatric patients, with variable clinical presentation. Despite a high incidence of steroid resistance among those with NS, an excellent response was observed with the addition of further immunosuppression.