Deletion Variants of <i>CFHR1</i> and <i>CFHR3</i> Associate with Mesangial Immune Deposits but Not with Progression of IgA Nephropathy.

Abstract

Activation of complement through the alternative pathway has a key role in the pathogenesis of IgA nephropathy (IgAN). Large, international, genome-wide association studies have shown that deletion of complement factor H-related genes 1 and 3 (<i>CFHR3,1Δ</i>) is associated with a reduced risk of developing IgAN, although the prognostic value of these deletions in IgAN remains unknown. Here, we compared the renal outcomes of patients with IgAN according to their <i>CFHR3,1Δ</i> genotype. This retrospective, monocentric cohort study included 639 white patients with biopsy-proven IgAN since 1979 (mean age at diagnosis, 40.1 years; median follow-up, 132 months). We determined the number of <i>CFHR3</i> and <i>CFHR1</i> gene copies by quantitative PCR and collected clinical and biologic data by reviewing the patients' medical records. In all, 30.5% of the patients were heterozygous and 4% were homozygous for <i>CFHR3,1Δ</i> We did not detect an association between <i>CFHR3,1Δ</i> and age, eGFR, urinary protein excretion rate, or the presence of hypertension or hematuria at the time of diagnosis. The mean intensities of immune IgA, IgG, and C3 deposits were lower in the group with heterozygous or homozygous gene deletions than in those with no deletion. However, <i>CFHR3,1Δ</i> did not associate with progression to stage 3 CKD or renal death. In conclusion, the <i>CFHR3,1Δ</i> genotype did not associate with progression toward CKD stages 3 and 5 in our white population of patients with IgAN, although it did associate with a reduced level of glomerular immune deposits.