1 Rheumatology Unit, University Hospital, Faculty of Medicine, Leipzig University, Liebigstrasse 20, 04103, Leipzig, Germany. Electronic address: Christoph.baerwald@medizin.uni-leipzig.de.
2 Head of Rheumatology and Translational Research, Director of Arthritis Research UK, Create Centre and Welsh Arthritis Research Network (WARN), Cardiff University School of Medicine, Division of Infection and Immunity, Tenovus Building, Heath Park, Cardiff, CF14 4XN, UK. Electronic address: choyeh@cardiff.ac.uk.