HLA-C and rheumatic disorder: Over time, a strong link between genetic predisposition and environmental factors has been demonstrated in several rheumatic diseases, and the Class I genes within the HLA system, such as HLA-A, HLA-B, and HLA-C, and the Class II genes, such as HLA-DQ, HLA-DR, and HLA-DP, all of which belong to the major histocompatibility complex (MHC), have been identified as promoters of these conditions [11,12].