To determine the clinical significance of anti-cyclic citrullinated peptide antibody (anti CCP) in mixed connective tissue diseases (MCTD).
Enzyme linked immunosorbent assay was performed to detect anti-CCP in 57 patients with MCTD, 78 with rheumatoid arthritis (RA), 64 with systemic lupus erythematosus (SLE), 56 with polymyositis/dermatomyositis (PM/DM), 53 with Sjögren syndrome (SS) and with 33 systemic sclerosis (SSc). The association between anti-CCP and clinical features of MCTD was analysed.
Anti-CCP was detected in 87.5% RA cases, 15.8% MCTD cases, 57.1% MCTD with RA cases, 14.1% SLE cases, 15.2% PM/DM cases, 18.9% SS cases and 9.1% SSc cases. Patients with RA (or MCTD with RA) were more likely to be anti-CCP positive than those without RA (P < 0.05). The MCTD patients with positive anti-CCP had higher prevalence of RA and SS related manifestations than those MCTD patients with negative anti-CCP (P < 0.05). The MCTD patients with RA had higher prevalence of RA-related symptoms, diffuse sclerosis and positive anti-CCP than those MCTD patients without RA (P < 0.01). Significant deviation of disease spectrum was found in the MCTD patients with RA compared with the anti-CCP positive MCTD patients without RA.
High titer of anti-CCP in combination with RA, SLE and SSc manifestations in MCTD patients can be an indicator of erosive arthritis.