Background/Purpose: Juvenile idiopathic inflammatory myopathies (JIIM) are potentially life-threatening systemic autoimmune diseases but little in known regarding factors associated with mortality.

Methods: Patients enrolled in a nationwide registry which included demographics, clinical and laboratory features, and outcomes. Timing of features (at diagnosis, after diagnosis or ever) was recorded. Mortality status was available for 419/441 (95%) patients (342 juvenile dermatomyositis (JDM), 30 juvenile polymyositis (JPM) and 47 juvenile connective tissue disease associated myositis (JCTM)), based on the Social Security Death Index or physician report. Poisson regression was used to assess univariable associations with mortality. Random survival forest classification followed by Poisson regression was used to assess multivariable associations.

Results: The cohort was 74% female, 69% white, median diagnosis age 7.6 years and median follow-up 4.3 years. There were 17 deaths (4%): 7 pulmonary (interstitial lung disease [ILD]), 3 gastrointestinal (perforation or hemorrhage), 3 multisystem (sepsis, multi-organ failure) and 4 unknown.

For univariable analysis, features present at diagnosis associated with an increased risk of death (P<0.05) were disease subgroup (mortality 2.3% JDM, 6.7% JPM, 14.9% JCTM), hospitalization, onset severity, younger age at diagnosis, anti-synthetase, anti-Ku or -La autoantibodies, dysphagia, abdominal perforation, Raynaud’s phenomenon, ILD, shawl sign rash, gastroesophageal reflux and dysphonia. Features present after diagnosis associated with an increased risk of death were wheelchair use at last assessment, ILD, fever, pneumothorax or pneumomediastinum, abdominal perforation and number of hospitalizations. For features present at any time, including unknown timing, additional features associated with increased risk of death included syncope, dyspnea, sclerodactyly, weight loss, and decreased risk: fatigue, Gottron’s papules and linear extensor erythema. Multivariable analyses revealed the following:

Conclusion: We have identified illness features associated with an increased risk of death in a large JIIM cohort. Some, such as ILD, anti-synthetase autoantibodies and Raynaud’s, extend to JIIM the factors that have been associated with mortality in adult disease.  Others, such weight loss, severity at onset, and fatigue (protective) are novel to this JIIM cohort. These results warrant further study in additional cohorts to confirm their predictive value.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/illness-features-associated-with-an-increased-risk-of-mortality-in-children-with-juvenile-idiopathic-inflammatory-myopathies/