Hemophagocytic Lymphohistiocytosis: Prevalence, Risk Factors, Outcome, and Outcome-related Factors in Adult Idiopathic Inflammatory Myopathies

To clarify the prevalence, risk factors, outcome, and outcome-related factors of hemophagocytic lymphohistiocytosis (HLH) in patients with dermatomyositis (DM), polymyositis (PM), or clinically amyopathic dermatomyositis (CADM).Data of patients with DM, PM, or CADM who were admitted to the First Affiliated Hospital of Zhejiang University from February 2011 to February 2019 were retrospectively collected. Patients diagnosed with HLH constituted the case group. A 1:4 case-control study was performed to identify risk factors for HLH in patients with DM, PM, or CADM through comparison, univariate, and multivariate logistic regression analysis. Intragroup comparison was made among patients with HLH to identify factors influencing unfavorable short-term outcome.HLH was a rare (4.2%) but fatal (77.8%) complication in patients with DM, PM, or CADM. The retrospective case-control study revealed that higher on-admission disease activity (p = 0.008), acute exacerbation of interstitial lung disease (AE-ILD, p = 0.002), and infection (p = 0.002) were risk factors for complication of HLH in patients with DM, PM, or CADM. The following intragroup comparison showed that higher on-admission disease activity (p = 0.035) and diagnosis of CADM (p = 0.039) might influence the short-term outcome of patients with HLH. However, no risk factor was identified after false discovery rate correction.In this study, secondary HLH was a fatal complication, with higher on-admission disease activity, AE-ILD, and infection working as risk factors. The underlying role of infection and autoimmune abnormality in HLH in connective tissue disease was subsequently noted. Clinical factors influencing the short-term outcome of patients with secondary HLH require further study.