Polymorphisms of CARD9 Gene Predict Disease Progression and Renal Survival of Immunoglobulin A Nephropathy

Introduction: A previous genome-wide association study has identified CARD9 (caspase recruitment domain family member 9) as a susceptibility gene for Immunoglobulin A nephropathy (IgAN), which encodes an adapter protein and is related to mucosal immunity. This study aims to investigate the association of CARD9 variants with the clinicopathological phenotypes and prognosis of IgAN. Methods: Eight SNPs within CARD9 were genotyped using Sequenom MassARRAY iPLEX for 986 IgAN patients in this study. Logistic and linear regression analyses adjusted for age and gender were performed to evaluate the effects of CARD9 gene polymorphisms on clinicopathological phenotypes. The Kaplan‒Meier method and Cox proportional hazard models were applied to analyse the associations between genetic variants and renal survival. Results: The T allele of rs10747047 was strongly associated with high levels of serum creatinine (P = 0.005) and the lower levels of estimated glomerular filtration rate (P = 0.005). The rs10870149-G and rs10870077-C allele were associated with elevated 24-h urine protein excretion (P = 0.041 and 0.022, respectively) and more serious segmental glomerulosclerosis lesions (P = 0.005 and 0.041, respectively) in IgAN patients. Carriers with the T allele of rs10781533 and the C allele of rs3812552 also presented with severe segmental glomerulosclerosis lesions (P = 0.001 and 0.010, respectively). Additionally, rs10747047-C and rs10870077-C alleles were independently related to the poor prognosis of IgAN patients after adjustments for covariates (TT vs. CC HR = 0.138, 95% CI = 0.022-0.871, P = 0.035; GG vs. CC HR = 0.321, 95% CI = 0.123, 0.836, P = 0.020, respectively). Conclusion: CARD9 variants are associated with disease severity and rapid disease progression for IgAN in a Chinese Han population.