CFHR5 and primary membranoproliferative glomerulonephritis: Our aim was to analyze the FHR-5 protein serum levels in a large group of IC-MPGN and C3G patients to better understand the possible role of the FHR-5 protein in disease pathogenesis or disease course and to screen the sequence of CFHR5. We also explored the connection of FHR-5 levels and CFHR5 variations with the recently described clinically relevant clusters in MPGN (4, 19, 38).