Background  Immune-mediated necrotizing myopathy (IMNM) is a newly recognized type of idiopathic inflammatory myopathy, however, there is no consensus on its treatment at present.

  Objective  To investigate the clinical characteristics of IMNM and the effect of different treatment strategies on its prognosis, and improve the understanding of IMNM in clinicians.

  Methods  Twenty-three eligible patients diagnosed as IMNM in the Department of Rheumatology of the First Medical Center of Chinese PLA General Hospital from October 2012 to October 2021 were enrolled in this study. The clinical characteristics of the patients were analyzed and the effects of different treatment strategies on CK (creatine kinase) levels and prognosis were compared.

  Results  A total of 23 patients were enrolled, in which 21 patients were female, and 2 patients were male, with an average age of (48.48±12.94) years. The most common characteristics of the patients were muscle weakness (95.65%, 22/23) and increased serum CK level (100%, 23/23). Nineteen cases (82.61%) had cardiac involvement, 13 cases (56.52%) with myalgia, 10 cases (43.48%) with dysphagia and 10 cases (43.48%) with interstitial lung diseases. The CK level decreased significantly both in the glucocorticoid pulse therapy (PT) group (n=11) and the non-pulse therapy (NPT) group (n=12) after treatment (P＜0.001), however there is no significant differences between the two groups at 1 month and 3 months after treatment (P>0.05). The 1-year overall response rate of the 23 IMNM patients was 65.22% (15/23), and no significant differences between the two groups were found (63.64% vs 66.67%, P=0.611).

  Conclusion  Glucocorticoid treatment at both pulse therapy group and non-pulse therapy group can effectively reduce CK level in IMNM patients. Cardiac involvement accounts for a high proportion in IMNM patients, and the current treatment strategies are effective for IMNM patients in general.