Risk stratification of severe infections after remission induction therapy in idiopathic inflammatory myopathy: a multicentre myko study

OBJECTIVES: To identify baseline predictors and develop a clinical risk stratification model for severe infections (SI) in patients with idiopathic inflammatory myopathy (IIM) after remission induction therapy. METHODS: We enrolled patients diagnosed with IIM between 1991 and 2024 from three Japanese centres participating in the multicentre Idiopathic Inflammatory Myopathy and Anti-synthetase Syndrome (MYKO) cohort. SI was defined as an infection requiring intravenous antibiotics or hospitalisation. We explored the risk factors for predicting SI in patients with IIM by comparing the initial demographic, clinical, laboratory, and treatments between the SI and non-SI groups. RESULTS: Among 349 patients with IIM, 14.6% of patients developed SIs after remission induction therapy over a median follow-up of 4.7 years. Patients who developed SI exhibited significantly lower baseline albumin levels, and significantly higher baseline C-reactive protein (CRP), lactate dehydrogenase, and surfactant protein (SP-D) levels than those without SI. Multivariate logistic regression analysis demonstrated that elevated CRP and SP-D levels were independently associated with SI. Serum CRP levels remained significantly higher in the SI group than in the non-SI group over the two-year period after immunosuppressive therapy, and the serum SP-D levels tended to be higher in the SI group. The 10-year SI rate was significantly different among patients with IIM stratified by the number of risk factors, defined as CRP ≥ 0.8 mg/dL and SP-D ≥ 96.2 ng/mL. CONCLUSIONS: This model, which consists of CRP ≥ 0.8 mg/dL, SP-D ≥ 96.2 ng/mL, is useful for clinical risk stratification of SI after remission induction therapy in IIM.