In conclusion, our study is the first to report observational data on serum FHR-5 levels at disease presentation and CFHR5 variations in a large group of IC-MPGN/C3G patients, where we observed that 14 patients (12.6%) were carriers of eight different CFHR5 variations (Table 3). Here, CFHR5 is linked to primary membranoproliferative glomerulonephritis.