Impact of allele copy number of polymorphisms in the FCGR3A and FCGR3B genes on susceptibility to Ulcerative Colitis

PurposeThe authors have previously shown three susceptibility loci to ulcerative colitis (UC), namely FCGR2A, 13q12, and SLC26A3 in a Japanese genomewide association study (GWAS). Top locus, FCGR2A located near the copy number variation (CNV) region of the FCGR gene cluster, which is associated with other autoimmune diseases including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). More recently, polymorphisms of FCGR3A-F158V and FCGR3B-NA1/2 in the CNV region have been reported to be associated with several autoimmune diseases and also to influence the response to infriximab in Crohn's disease and RA. However, most of these reports had not taken into account for the effect of CNV in the FCGR region. The presence of common CNVs can cause miss classification of subjects and false genotyping results. Here, we investigated possible combined effect of polymorphisms and copy number in the FCGR gene cluster, namely, FCGR3A-V158F and FCGR3B-NA1/2 on the occurrence of UC.