1 Department of Internal Medicine 3-Rheumatology and Immunology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany.
2 Department of Rheumatology and Clinical Immunology, Charité - Universitätsmedizin, Berlin, Germany.
3 Department of Internal Medicine 3-Rheumatology and Immunology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany. johannes.knitza@uk-erlangen.de.