1. Department of Medicine II, Hokkaido University School of Medicine, N-15, W-7, Kita-ku, Sapporo 060-8638, Japan Department of Medicine II, Hokkaido University School of Medicine, Sapporo, Japan
2. Department of Medicine II, Hokkaido University School of Medicine, Sapporo, Japan; Division of Rheumatology, Department of Internal Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan
3. Department of Medicine III, Obihiro Kousei Hospital, Obihiro, Japan
4. Department of Medicine II, Hokkaido University School of Medicine, Sapporo, Japan