C1q nephropathy (C1qN) is a rare glomerulopathy mostly seen in children, and presents with nephrotic syndrome (NS). Diagnosis depends on immunoflourescence or immunohistochemical C1q mesangial deposition, excluding other immune-mediated diseases. We retrospectively investigated C1qN incidence, clinicopathological features, and outcome among pediatric NS in our institution.Clinical data, microscopic slides and corresponding tissue blocks of pediatric renal biopsies were retrieved. According to diagnostic criteria for C1qN, 53 pediatric NS renal biopsies were selected for Anti-C1qA IHC stain microscopic examination. Clinicopathological features and follow up data were recorded. C1qN incidence was 9.4% among pediatric NS biopsies. Mesangial proliferation was the most common histopathological pattern. Steroid dependency with frequent relapses was the most frequent outcome, with a second line immunosuppressant added, yet without impact on progression. Small sample size hinders coherent conclusions; nevertheless, it indicates that C1qN is a rare cause of pediatric NS. C1qN may require second line immunosupressants more often than non-C1q NS.

Keywords: C1q nephropathy, glomerulonephritis, nephrotic syndrome