Overlap between systemic sclerosis and rheumatoid arthritis: a distinct clinical entity?

Alex Magno Coelho Horimoto, Izaias Pereira da Costa

Systemic sclerosis (SSc) is an autoimmune disease of the connective tissue characterized by the triad of vascular injury, autoimmunity (cellular and humoral) and tissue fibrosis. It is estimated that musculoskeletal pain is a common complaint of patients with SSc, ranging from 40 to 80%, and mainly in patients with early diffuse disease. Arthritis, clinically observed, may be a feature seen in the presentation of SSc, often leading to early diagnostic errors with rheumatoid arthritis (RA). In the course of the disease, arthritis is observed in 24-97% of patients with SSc. To correlate the occurrence or nonoccurrence of arthritis in patients with SSc of the Midwest region of Brazil with possible distinct clinical and laboratory manifestations observed in three groups of patients. To report the frequency of true association between systemic sclerosis and rheumatoid arthritis in patients with clinically and radiologically observed synovitis. Sixty-one SSc patients were subsequently assessed every 3 months within 1 year, in order to clinically observe the occurrence of synovitis and its patterns of progression. Patients were divided into 3 groups: 41 patients with SSc without arthritis, 16 SSc patients with arthritis and 4 patients with overlap of SSc and RA. All patients underwent a radiological examination of the hands at the end of the study. Among all patients evaluated, we found a female predominance (98.7%), mean age of 50.94 years, white color (49.2%), limited form of the disease (47.6%), time of diagnosis between 5 and 10 years (47.6%) and duration of the disease of 8.30 years. Among all patients, 14 (22.9%) had positive rheumatoid factor (RF), while among those with positive RF, only 10 patients had arthritis during one-year follow-up. The antibody anticitrulline (anti-CCP) test was performed in 24 patients, being positive in 4 of them (16.7%), with positivity being observed only in patients with SSc/RA overlap. Comparing the clinical manifestations among the groups of patients, there was a higher incidence of gastritis and cardiac valvulopathy in patients with SSc and arthritis, but not in the others. In the group of patients with SSc/RA overlap and in patients with SSc and arthritis a significant reduction in quality of life was observed, measured by HAQ index, especially in patients with arthritis present during clinical evaluation. We found radiographic changes in 42.6% of patients with SSc. However, in patients with synovitis, radiological changes consistent with rheumatoid arthritis were found in 50% of patients. While the frequency of clinical arthritis observed in patients with systemic sclerosis was 32.8%, the true overlap between of SSc and RA was 6.6% in this study. We also observed the frequency of positive anti-CCP in 20% of patients with arthritis versus no patients with SSc without arthritis.