Treatment of mixed connective tissue disease: A multicenter retrospective study.

Introduction: Mixed connective tissue disease (MCTD) is a rare systemic disorder that belongs to connective tissue diseases (CTD). Few studies are available on MCTD treatment.

Methods: We conducted an observational study within the French MCTD cohort. Data were collected at diagnosis, during follow-up, and at the last follow-up (LFU). We studied three treatment groups i) no treatment, ii) hydroxychloroquine (HCQ) and/or glucocorticoids (GC) and iii) disease-modifying antirheumatic drugs (DMARDs)/immunosuppressant (IS).

Results: Three hundred and fifteen patients were included and followed for 96 [40-156] months. At MCTD diagnosis, 52 (16.5 %) patients were treatment-free, while 224 (71.1 %) received GC and/or HCQ and 39 (12.4 %) received DMARDs and/or IS. During follow-up, 10 (3.2 %) patients remained treatment-free, and 77 (24.4 %) were GC-free. Most patients (n = 271; 85.8 %) received HCQ, and 161 (51.1 %) were treated with DMARDs and/or IS. DMARDs and/or IS, including anti-B cell therapeutics, were more frequently prescribed in patients with musculoskeletal involvement (p < 0.0001), interstitial lung disease (ILD, p < 0.0001) and/or pulmonary arterial hypertension (PAH, p < 0.01). Patients in clinical remission and those who did not evolve to a differentiated CTD (MCTD-dCTD) received significantly less frequently DMARDs and/or IS (including anti-B cell therapeutics; p < 0.0001 for both). Patients who received HCQ at MCTD diagnosis appeared to develop less frequently ILD or PAH (p < 0.05).

Conclusion: HCQ and GC were the cornerstones of MCTD treatment and were sufficient to control disease manifestations in nearly half of the patients, reflecting the good prognosis of this disease. DMARDs and IS were used for musculoskeletal involvement, PAH/ILD, and in MCTD-dCTD patients.