Rheumatoid Arthritis (RA) is a chronic inflammatory polyarthritis disease predominantly involving synovial tissue of the joints and characterized by destructive and debilitating arthritis (Choy et al., 2012; Weyand, 2000; reviewed by Worthington, 2005; Gabriel et al., 1999). It can cause progressive and irreversible destruction of tendons, cartilage and bone, which leads to lack of ability to perform daily activities (Singh et al., 2015). Although the aetiology of RA remains unsolved, the strength of the genetic component in RA is estimated based on familial aggregation and information about epidemiology and population prevalence (reviewed by Gregersen, 1999, Choy et al., 2012). (Copied from article).