Background: It is found that an antibody directed against DNA topoisomerase I (anti-topo I abs) is detected almost exclusively in systemic sclerosis (SSc). These antibodies are predictors of pulmonary fibrosis and peripheral vascular disease.
Objective: Metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints flexion contractures are assessed as markers of active SSc. The aim of this study was to find out is there any relationship between anti-topo I abs and MCP and PIP joints flexion contractures.
Methods: Twenty-eight patients with active disease who fulfilled the American College of Rheumatology criteria for SSc were included in this study. Twenty eight healthy control subjects were also investigated. Clinical and radiological assessments of the hands were carried out. The flexion ranges in the 8 finger joints by goniometric measurement were obtained. Anti-topo I abs with an enzyme linked immunosorbent assay (ELISA) were measured.
Results: MCP and PIP joints flexion contractures and the levels of anti-topo I abs were significantly higher in patients with systemic sclerosis than in healthy control. The anti-topo I abs were found in 16 of 28 patients with systemic sclerosis. Sixteen of 28 patients with active disease had MPC and proximal PIP joints flexion contractures. In 16 SSc patients with anti-topo I abs, 13 had metacarpophalangeal and proximal interphalangeal joints flexion contractures. In only 3 patients of 16 with the flexion contractures the levels of anti-topo I abs were negative. The patients with MPC and PIP joints flexion contractures had higher mean value of anti-topo I abs titers (53.718 +/-50.977 vs 8.127 +/- 8.915, P < 0.0001) than did those with no contractures. Furthermore, the titers of anti-topoisomerase I antibody positively correlated with the flexion contractures (r = 0.4252, P = 0.0241). Radiologically, joint space narrowing and flexion contractures of the fingers were seen significantly more frequently in the SSc patients with anti-topo I abs (P < 0.05).
Conclusion: Serum level of anti-topoisomerase I antibodies is in direct relationship with MPC and PIP joints flexion contractures.