A new age has begun in the genetics of rheumatoid arthritis (RA), as genome-wide 
association studies scanning the human genome have been put into practical use. 
Among the RA-susceptibility genes identified by genetic studies, HLA-DRB1 gene 
appears to represent the most major determinant of genetic predisposition to RA. 
However, inconsistent results of the contributions of non-HLA susceptibility 
genes have been described, with the exception of a few genes repeatedly 
associated with RA-susceptibility, such as PTPN22 gene in populations of 
European ancestry and PADI4 gene in populations of Asian ancestry, revealing the 
presence of genetic heterogeneity in RA. We review herein recent advances in the 
genetics of RA and discuss the underlying differences among populations of 
European and Asian ancestries, taking as examples our previous findings for 
RA-susceptibility genes in the Japanese population: PADI4; FCRL3; and CD244.