Relapse risk factors and clinical characteristics of idiopathic inflammatory myopathies in 105 patients.

Objective: To identify the risk factors for relapse of idiopathic inflammatory myopathies (IIMs).

Methods: Patients who were newly diagnosed with IIMs and underwent muscle biopsy between 2000 and 2017 at Asan Medical Center were retrospectively reviewed. The relapse of IIMs was defined as the recurrence of muscle or cutaneous manifestations with a ≥50% increase in glucocorticoid dosage after reaching the low-dose glucocorticoid phase with clinically significant improvement. The factors associated with the relapse of IIMs were investigated by Cox proportional hazards analysis.

Results: Of 105 patients with IIMs, relapse was observed in 65 patients (62%). The titer of antinuclear antibody (ANA) was higher in the relapse group than in the non-relapse group (P = 0.033). Multivariable analysis showed that the relapse of IIMs was significantly associated with histopathologic features consistent with IIMs (hazard ratio [HR], 1.69; 95% confidence interval [CI], 1.01-2.83, P = 0.045) and the use of immunosuppressants before relapse (HR, 0.50; 95% CI, 0.29-0.86, P = 0.013). Doubling of ANA titer was also associated with relapse, albeit without statistical significance (HR, 1.13; 95% CI, 1.00-1.27, P = 0.052).

Conclusion: In patients with IIMs, the use of immunosuppressants had a significant negative association with relapse. Administering immunosuppressants from the early period during the initial glucocorticoid tapering phase may be useful in reducing the risk of relapse in patients with IIMs. Key Points • Since idiopathic inflammatory myopathies (IIMs) have a low prevalence, it is poorly understood which factors are associated with the relapse of IIMs. • In this study, about two-thirds of 105 patients with IIMs experienced a relapse of IIMs. • The risk of relapse in patients with IIMs was negatively associated with the use of immunosuppressants during glucocorticoid tapering and low-dose glucocorticoid phase. • Even in less severe cases, the use of immunosuppressants might be a good option for the management of IIMs.