1. Policlinic and Hiller Research Unit for Rheumatology, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
2. Division of Rheumatology and Inflammatory Rheumatic Diseases, University Hospital Hamburg-Eppendorf, Hamburg, Germany
3. Department of Rheumatology and Clinical Immunology, Charité –Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany