Hepatitis B virus (HBV) is a common viral infection in humans, and HBV infection is endemic in Taiwan. 1 Rheumatoid arthritis (RA) is characterized by chronic inflammation of the joints resulting in deformity and disability. Common medications for the treatment of RA include: (a) conventional synthetic disease-modifying antirheumatic drugs (csDMARDs); (b) biologic agents, such as tumor necrosis factor inhibitors, abatacept, rituximab, tocilizumab; and (c) targeted synthetic DMARDs, such as tofacitinib, baricitinib,