Comparison of articular manifestations of mixed connective tissue disease and systemic lupus erythematosus on clinical examination and musculoskeletal ultrasound.

BACKGROUND

Polyarthritis is common to both mixed connective tissue disease (MCTD) and systemic lupus erythematosus (SLE). Apart from being erosive and deforming in the former, we speculated that it was more common and the extent of joints involved would be higher in MCTD.

METHODS

This was a cross-sectional study that included patients with MCTD aged 18-75 years fulfilling the Kasukawa criteria. An equal number of patients with SLE matched for disease duration and gender were included. Clinical manifestations were compared between patients with MCTD and with SLE. Examination of joints was done for the presence of tenderness or swelling and deformity. Musculoskeletal ultrasound was done on the non-dominant hand for detection of synovitis and tenosynovitis and radiographs of the hands were obtained. The use of methotrexate and non-steroidal anti-inflammatory drugs (NSAIDs) for arthritis was noted. Statistical tests used were non-parametric.

RESULTS

Forty patients with MCTD and forty patients with SLE were included in this study, with patients being slightly older in MCTD than SLE (36 ± 10.2, 31.8 ± 13.3 years, p = 0.01). There were no significant differences in disease duration (4.7 ± 3.1, 3.7 ± 2.3, p = 0.1) or gender (females = 38, 38). Nearly one-half of patients with MCTD had at least one swollen joint compared with only 15% of patients with SLE. Median (95% confidence interval) tender joint count (5 (4.8-10.4), 0 (1.3-7.2), p = 0.01) and swollen joint count (0 (0.9-2.6), 0 (0-1.2), p = 0.002) was significantly higher in patients with MCTD compared with SLE. More patients with MCTD than SLE had tender or swollen proximal interphalangeal joints (12, 4, p = 0.025). More patients with MCTD than SLE had received methotrexate (8,2, p = 0.04) and NSAIDs (39, 32, p = 0.03) for arthritis. There was no difference in the number of patients with MCTD or SLE who had evidence of synovitis or tenosynovitis on ultrasound. There was no difference in erosive disease on hand radiographs, but acro-osteolysis was higher among MCTD patients.

CONCLUSIONS

A higher proportion of patients with MCTD had at least one swollen and tender joint as compared with patients with SLE, as well as higher use of methotrexate and NSAIDs. However, there was no difference in ultrasound detected synovitis or tenosynovitis.