IgA nephropathy (IgAN) is a common cause of glomerulonephritis and a major cause of end stage renal disease in up to 20-40% of patients. However, its prognosis still cannot be accurately predicted due to the high heterogenicity of clinical presentations and courses. Complement dysregulation is a main driver of glomerular damages in many glomerulonephritis. Given the growing body of evidence of complement lectin/alternative pathways activation in IgAN pathogenesis, the investigators propose the evaluation of a combination of biomarkers of infra-clinical complement activation to stratify the risk of disease's progression. This study aims to identify subsets of patients in whom complement activation plays a critical role in disease progression. This is of particular interest in the aera of emergence of complement-targeting therapies in IgAN
ICONE study (IgA Complement and NEphropathy is a prospective monocentric observational study.~The main objective is to evaluate the relevance of complement activation as a biomarker of disease severity and progression in patients with a biopsy proven IgAN.