Background Mixed connective tissue disease (MCTD) has been considered to have a good prognosis, although some patients present severe clinical manifestations like pulmonary hypertension.
Objectives To compare the cumulative tissue damage occurring in patients with MCTD and systemic lupus erythematosus (SLE).
Methods We compared the cumulative tissue damage index scores of patients with MCTD and SLE studied between 1988 and 2000. The consequences of MCTD and SLE and their treatment were evaluated using the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SLICC/ACR) obtained at the last follow-up visit; scleroderma lesions were not taken into account in patients with MCTD.
Results We studied 37 patients with MCTD and 236 patients with SLE. There was no difference in the relative proportion of women in with MCTD and SLE (32 of 37; 86.5% vs 211 of 236; 89.4%). Mean age (40 years; SD 17.6 vs 39; SD 15.8), mean age at onset of disease (29 years; SD 17.6 vs 29; SD 14.7), and mean duration of disease (11 years; SD 7.9 vs 9.7; SD 6.9) were similar in both groups. There were no differences in mortality (1 of 37; 2.9% vs 8 of 236; 3.4%) or SLICC score (1.43; SD 1.11 vs 1.49; SD 1.88). Patients with MCTD had more musculoskeletal sequelae (20 of 37; 54.1% vs 36 of 236; 15.3%) (OR: 6.5) (p < 0.005) and pulmonary fibrosis (5 of 37; 13.5% vs 9 of 236; 3.8%) (OR: 3.9) (p < 0.05) than patients with SLE. Patients with SLE had more kidney disease as defined by the SLICC (66 of 236; 28% vs 3 of 37; 8.1%) (p < 0.01).
Conclusion In spite of the differences observed, the cumulative tissue damage and mortality were similar in MCTD and SLE, after excluding from consideration scleroderma lesions in patients with MCTD.