Background/Purpose: Idiopathic inflammatory myopathies (IIM) are heterogeneous disorders characterised by skeletal muscle weakness and muscle inflammation. IIM includes dermatomyositis (DM), polymyositis (PM), antisynthetase syndromes (ASS), scleromyositis (SCM), inclusion body myositis (IBM), immune-mediated necrotizing myopathies (IMNM) and Overlap Syndromes (OS). Previous population-based studies have demonstrated a higher risk of venous thromboembolism (VTE) in IIM patients compared to healthy controls. In these works, IIM were only divided in PM and DM and few risk factors of VTE have been highlighted. The purpose of this study was to identify the VTE specific risk factors in IIM and analyse VTE occurrence in more recently defined subtypes of IIM.

Methods: All adults with IIM hospitalized in Internal Medicine units from Eastern France between 2004 and 2018 were enrolled. Demographic, clinical and laboratory data were retrospectively collected from medical records. Mann-Whitney test and Chi-square test were used for comparison of continuous and discrete variables, respectively. We computed a multivariate model to determine factors associated with VTE using a Cox analysis. VTE-free survival analysis was performed using log-rank test.

Results: 203 patients (55 male, 148 female) were involved. The mean age at diagnosis was 51 years +/-16. VTE occurred in 12% of cases, mostly within the first year of follow-up (31%). At VTE diagnosis, conditions such as immobilization (20%), infection (10%), malignancy (20%), active disease (31%), treatment by intravenous immunoglobulins (17%) or by glucocorticoids (55%) were observed. In univariate analysis, we found that patients with VTE experienced more dysphonia (p=0.037) and received a greater number of therapeutic lines (p=0.035) compared to patients without VTE. In multivariate analysis, significant risk factors were personal history of pulmonary embolism (HR 13, p=0.023), dysphonia (HR 99, p=0,00005), elevated C-reactive protein (HR 5.1, p=0.0081) and number of therapeutic lines (HR 2.7, p=0.023). We compared VTE-free survival in all IIM subtypes within the five years after diagnosis: a particular subgroup including DM, PM, ASS, OS and IMNM (group 1) presented a higher risk than another including SCM, IBM and unspecified myositis (group 2) (HR 4.21, p=0,048).

Conclusion: Common but also unexpected risk factors were reported here. Elevated C-reactive protein confirmed the link between inflammation and thrombosis mechanisms. Dysphonia and the number of therapeutic lines reflected a more severe disease. Among IIM, only those in group 1 (DM, PM, ASS, OS and IMNM) were associated with an increased risk of VTE. The identification of these subtypes should alert to VTE risk and lead to early apply prophylactic measures.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-factors-of-venous-thromboembolism-in-idiopathic-inflammatory-myopathies/