Methods: The records of patients with inflammatory myopathy who had previously failed treatment with at least one immunosuppressant were retrospectively evaluated. We selected patients treated with MMF and divided them into two groups depending on whether or not there was concomitant use of CNIs. We investigated the efficacy by changes in creatine kinase (CK) levels, forced vital capacity (%FVC), and PSL dose. Deterioration was defined as death or drug change due to treatment failure.

Results: We identified 19 patients (14 for DM and 5 for PM) on MMF treatment. There were seven (36.8%) patients on MMF and CNIs, including five on cyclosporine and two on tacrolimus. Average observational periods were 18.6 (SD: 20.5) months in those with the MMF and CNIs and 14.3 (SD: 13.7) months in patients with MMF (P = 0.29). At baseline no significant difference in clinical features including the prevalence of interstitial lung disease (ILD) was seen in between patients taking or not taking CNIs (Table 1). Improvement in CK was seen in patients treated with CNIs (P = 0.04) but not in those without (P = 0.39). No significant improvement in %FVC was found in patients with ILD in either group, and patients with CNIs had a slightly better result than those without in deterioration rate but no differences was seen (P = 0.62) (Figure 1).

Conclusion: The combination of CNIs and MMF might be more effective for decreasing CK levels than MMF alone. Neither treatment arm had a beneficial effect on ILD or deterioration rate over a short-term observation.