title: Preface.
authors.affiliation: Dept. of Rheumatology, Sint Maartenskliniek, PO Box 9011, 6500 GM, Nijmegen, The Netherlands. Electronic address: A.denbroeder@maartenskiniek.nl.
authors.forename: Alfons A
authors.initials: AA
authors.lastname: den Broeder
authors.affiliation: David Geffen School of Medicine, Division of Rheumatology, University of California, Los Angeles, USA.
authors.forename: Thasia G
authors.initials: TG
authors.lastname: Woodworth