1 Medical Faculty, Department of Rheumatology and Hiller Research Unit Rheumatology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany philipp.sewerin@med.uni-duesseldorf.de.
2 Medical Faculty, Department of Rheumatology and Hiller Research Unit Rheumatology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.