HLA-C and rheumatoid arthritis: The coding region of GABA type B receptor subunit (GABBR)-1 is located on chromosome 6, 6p21.3, and the major histocompatibility complex (MHC) located in this region is associated with multiple sclerosis, Alzheimer’s disease, schizophrenia, narcolepsy, epilepsy, and RA (81).