Copy number variation of FCGR3A rather than FCGR3B and FCGR2B is associated with susceptibility to anti-GBM disease.

Anti-glomerular basement membrane antibody disease (anti-GBM disease) is a rare disorder characteristic of universally poor outcome. Fcgamma receptors (FcgammaRs) play important roles in anti-GBM disease based on evidence from animal models. Copy number variation (CNV) influences disease susceptibility. The FcgammaRs genes show CNV, and CNV of the FCGR3B gene is associated with glomerulonephritis in systemic lupus erythematosus and anti-neutrophil cytoplasmic antibody-associated small vasculitis. Here, we investigated CNV of three FCGR genes, including two (FCGR3A and FCGR3B) for activating FcgammaRs and one (FCGR2B) for inhibitory FcgammaR by duplex quantitative real-time PCR. Copy numbers were analyzed by Applied Biosystems CopyCaller Software v1.0. We first demonstrated the distribution of CNV of FCGR3A, FCGR3B and no CNV of FCGR2B in Chinese population (including 47 anti-GBM patients and 146 healthy controls). The frequency of CNV of FCGR3A was observed to be significantly higher than matched healthy controls (27.7 versus 12.3%, P = 0.013, odds ratio 1.21-6.10). Considering previous report about gene knock-out animal models and CNV effect of FCGR3A, we thus propose that CNV in members of FCGR family should have different roles in the pathogenesis of human anti-GBM disease.