Footnotes

• Handling editor Josef S Smolen

• Contributors TM, MS and JK treated the patients and wrote the manuscript; MH, MM diagnosed and treated the patient, and provided important opinions on the manuscript.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests TM received research funding from MSD KK, Novartis Pharma, LSI Medience, Medical & Biological Laboratories, and Asahi Kasei Corporation, and personal fees from Pfizer, MSD, Janssen Pharma, Sumitomo Dainippon Pharma, Novartis Pharma, Kyowa Kirin, Chugai Pharmaceutical, Shionogi, Japan Blood Products Organization, Takeda Pharmaceutical, Ono Pharmaceutical, Shire, Eisai, and Astellas Pharma; MM received research funding from Chugai Pharmaceutical, UCB Japan, CSL Behring, Abbvie Japan, Japan Blood Products Organization, Ayumi Pharmaceutical, Nippon Kayaku and Asahi Kasei, personal fees from MSD KK, and consulting fees from Daiichi Sankyo, and Taisho Pharmaceutical.

• Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

• Patient consent for publication Obtained.

• Provenance and peer review Not commissioned; externally peer reviewed.