Japan College of Rheumatology guideline for the use of methotrexate in patients with rheumatoid arthritis.

Methotrexate (MTX), the anchor drug in the current treatment strategy for rheumatoid arthritis (RA), was first approved for treatment of RA in Japan in 1999 at the recommended dose of 6-8 mg/week; it was approved as first-line drug with the maximum dose of 16 mg/week in February 2011. However, more than half of Japanese patients with RA are unable to tolerate a dose of 16 mg/week of MTX. Moreover, some serious adverse events during the treatment with MTX, such as pneumocystis pneumonia (PCP) and lymphoproliferative disorders (LPD) have been observed much more frequently in Japan than in other countries. Therefore, this article, an abridged English translation summarizing the 2016 update of the Japan College of Rheumatology (JCR) guideline for the use of MTX in Japanese patients with RA, is not intended to be valid for global use; however, it is helpful for the Japanese community of rheumatology and its understanding might be useful to the global community of rheumatology.