To determine the incidence of patients with both systemic sclerosis and rheumatoid arthritis (SSc-RA) and the clinical features of those with SSc-RA.
All 173 patients with systemic sclerosis in our clinic were investigated.
Of the 173 patients with systemic sclerosis, 9 (5.2%) developed rheumatoid arthritis (RA). At the first visit, arthritis prior to Raynaud's phenomenon, increased C-reactive protein (CRP), and elevated rheumatoid factor (RF) were seen in patients with SSc-RA at a significantly higher incidence than in those without (44.4% versus 4.8%, p < 0.01; 55.6% versus 13.6%, p < 0.001; 247.2 +/- 312.1 versus 47.9 +/- 54.3 IU/ml, p < 0.001, respectively). Furthermore, in 8 of the 9 patients with SSc-RA, CRP was increased before the diagnosis of RA.
These results suggest that systemic sclerosis patients with elevated RF and a history of arthralgia prior to Raynaud's phenomenon should be followed up with serial measurements of CRP due to their risk of developing RA.