title: Anticyclic citrullinated peptide antibodies in patients with mixed connective tissue disease.
abstract: The clinical significance of anticyclic citrullinated peptide (CCP) antibodies in patients with mixed connective tissue disease (MCTD) was assessed. Altogether, 86 sera from MCTD patients, 96 from rheumatoid arthritis (RA) patients, 42 from systemic lupus erythematosus (SLE) patients, 23 from systemic sclerosis (SSc) patients, 21 from polymyositis/dermatomyositis (PM/DM) patients, and 17 from those with Sjögren's syndrome (SjS) were tested for anti-CCP antibodies using an enzyme-lined immunosorbent assay. Among the 96 RA patients, anti-CCP antibodies were detected in 85%, with the frequency being significantly higher than in MCTD, SLE, SSc, PM/DM, and SjS patients (9%, 14%, 13%, 14%, and 18%, respectively; P < 0.001). Among eight MCTD patients who fulfilled the diagnostic criteria for RA, only 50% had anti-CCP antibodies, and the prevalence was significantly lower than for all RA patients (p < 0.01). All eight patients who fulfilled the criteria for RA had overlap of SLE and SSc, except one patient, whereas the four anti-CCP-positive patients who did not fulfill the criteria for RA had SjS without overlapping features of SLE and SSc; moreover, most of their antibody titers were low. These results suggested that anti-CCP antibodies are associated with RA in MCTD patients, but careful diagnosis of RA is required if patients with low titers of anti-CCP antibodies lack overlapping SLE and SSc.
authors.affiliation: Department of Internal Medicine and Rheumatology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. tyoshi@med.juntendo.ac.jp
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Takasaki
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Yamanaka
authors.forename: Chiho
authors.initials: C
authors.lastname: Takasaki
authors.forename: Masakazu
authors.initials: M
authors.lastname: Matsushita
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yamada
authors.forename: Masuyuki
authors.initials: M
authors.lastname: Nawata
authors.forename: Ran
authors.initials: R
authors.lastname: Matsudaira
authors.forename: Keigo
authors.initials: K
authors.lastname: Ikeda
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kaneda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto