HLA-DRB1 and juvenile idiopathic arthritis: The HLA-RB5 gene is in the HLA region of chromosome 6p21.31, and various studies have identified the HLA gene region as a major susceptibility locus for JIA, including HLA class I (HLA A-2, and HLA B27) and HLA class II (HLA-DRB1 and HLA DP) genes (40, 41).