Background: There has been no prior inception cohort study comparing clinical manifestations and incidence rate (IR) of cardiopulmonary involvement among early systemic sclerosis (SSc) patients by difference in autoantibody profiles. We compared the differences in the clinical presentation at study entry and cumulative organ complications at last visit, as well as the IR of cardiopulmonary complications between anti-topoisomerase I antibody-positive SSc patients (pATA), ATA-negative (nATA), and the positive anti-centromere antibody patients (pACA).
Methods: An inception cohort of early diagnosis SSc patients (disease duration ≤ 3 years) seen at the Rheumatology Clinic, Maharaj Nakorn Chiang Mai Hospital, between January 2010 and June 2016, was studied. SSc patients who had follow-up duration as less than 1 year and those diagnosed with an overlap syndrome were excluded. All participants underwent electrocardiography (ECG), echocardiography, and high-resolution computed tomography (HRCT) at the study entry and then annually.
Results: A total of 114 patients (90 diffuse cutaneous SSc (dcSSc), 69 women) with mean (standard deviation, SD) disease duration of 11.7 (8.8) months at cohort entry and an observational period of 3.8 (1.6) years, were recruited. There were 89 patients (78.1%) with pATA, 18 (15.8%) with nATA, and 7 (6.1%) with pACA. At enrollment, both pATA and nATA groups had a higher prevalence of dcSSc subtype, and interstitial lung disease (ILD) when compared with the pACA group. At the last visit, the pATA group had a higher cumulative prevalence of digital ulcers, joint contracture and tendon friction rub than the other groups. Both the pATA and nATA groups had a significantly higher IR of ILD compared to the pACA group (54.9 and 57.8 vs. 6.3 per 100 person-years). During the study period, no suspected myositis, systolic pulmonary artery pressure (sPAP) ≥ 50 mm Hg or cardiac complications was observed in the pACA group.
Conclusions: In our study cohort, the majority of which were dcSSc subtype with pATA, it was found that the presence of SSc-specific autoantibodies was associated with a distinctive clinical presentation and cumulative internal organ involvement, even in the early phase of the disease. Cardiopulmonary complications were rarely seen in the pACA group; whereas ILD complications were very common in both the pATA and nATA groups. A further study into the association of autoantibodies in nATA patients with ILD complications is needed.
Keywords: Anti-centromere antibody; Anti-topoisomerase I antibody; Clinical manifestation; Incidence; Systemic sclerosis.