1 Department of Rheumatology and Clinical Immunology, Sapporo Medical University School of Medicine, South 1-West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan. nagahata.ken@sapmed.ac.jp.
2 Department of Rheumatology and Clinical Immunology, Sapporo Medical University School of Medicine, South 1-West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.