Background the overlap syndrome Systemic sclerosis-rheumatoid arthritis (SSc-RA) is characterized by the presence in the same patient of clinical and laboratory features that meet the classification criteria for both diseases. The current literature shows how that lung involvement is more frequent and severe in SSc-RA than in SSc alone .
Objectives to describe the frequency of clinically significant interstitial lung disease (ILD), determining the reduction of the forced vital capacity (FVC) or the alveolar-capillary diffusion of carbon monoxide (DLCO) in a group of 25 patients with SSc-RA compared to a control group of 570 patients with SSc alone.
Methods data were retrieved from a database and from medical records of patients followed at the outpatient clinic dedicated to SSc of the Rheumatology Unit of S. Anna Hospital, Ferrara. All patients fulfilled the classification criteria for SSc (ACR 1980 and LeRoy 2001) and RA (1987). For both groups (SSc and SSc-RA) the following seroimmunologic data were assessed: anticentromere antibodies (ACA), anti topoisomerase 1 (Scl 70), rheumatoid factor (RF) and anti-citrulline (ACPA). Pulmonary involvement was assessed by high-resolution chest CT scan using the score of Warrick, and spirometry including DLCO. A cut-off of Warrick's score able to detect patients with ILD has been identified by the application of a regression curve between the total score at HRCT and spirometry data (FVC and/or DLCO <75% as predicted); the analysis identified a value>10 able to alter lung function.
Results in the SSc control group FR was available in 38% of cases and ACPA only in 8.9% RF and ACPA were available in all 25 SSc-RA patients. Positivity for both FR and ACCP was detected in 23 SSc-RA patients whilst 2 were seronegative. ILD was more frequent in SSc-RA group compared to SSc (76% VS 33%, p<0.05, OR 6.43). The SSc-RA/ACA + group presented a higher frequency of ILD than in SSc/ACA + (54.5% VS 21.7%, p<0.05, OR 4:33) as if the known protective role of the ACA for the development of ILD was less relevant in SSc-RA. In the SSc group, the positivity of the RF seems to be associated with the risk of developing ILD only in patients ACA/Scl 70 negative (72% vs. 28%, p<0.05, OR 6.3). Due to missing data it was not possible to perform the analysis for the ACPA in SSc group.
Conclusions an increased risk of ILD in SSc-RA compared to SSc was confirmed. In SSc-RA group, ACA seems to lose its role as a “protective” factor against the possible development of pulmonary fibrosis. If this information is confirmed, in SSc-RA patients, despite their ACA positivity, it could justify a more “tight” clinical-instrumental follow-up, to detect lung involvement early and to monitor its evolution.
Systemic sclerosis-rheumatoid arthritis overlap syndrome: a unique combination of features suggests a distinct genetic, serological and clinical entity. Szücs G, Szekanecz Z, Zilahi E et al. Rheumatology (Oxford). 2007 Jun;46(6):989-93
Disclosure of Interest None declared