FCGR3B and rheumatoid arthritis: Low copy number and the deletion of FCGR3B increase the risk of RA (Tsang-A-Sjoe et al., 2016; Wang et al., 2016b; Rahbari et al., 2017; Zheng et al., 2017), and FCGR3B gene copy number has also been suggested to increase susceptibility to UC, which indicates that FCGR3B might be the key gene involved in their pathogenesis (Asano et al., 2013).