Objective: To characterize the metabolic abnormalities and risk factors for future cardiovascular disease in children with myositis.
Study design: Seventeen patients with severe juvenile myositis, primarily referred because of refractory disease, were examined with standardized disease activity and damage measures. Body mass index, fasting insulin and lipid levels, 2-hour oral glucose tolerance test results, and cytokine levels were obtained.
Results: Most patients (71%) had blood pressures >75th percentile; 23.5% of patients had hypertension; and body mass index was >85th percentile in 47%. Metabolic abnormalities were also frequent: 41.2% had an elevated fasting insulin level, 47.1% had hypertriglyceridemia, and 25% met criteria for the metabolic syndrome. Although insulin resistance was common (on the basis of homeostasis model assessment and glucose-to-insulin ratio), insulin secretion appeared to be unaffected. Thigh muscle damage assessed with magnetic resonance imaging significantly correlated with fasting insulin level, glucose level, and glucose-to-insulin ratio. Glucose indices also correlated with the proinflammatory cytokines interleukin (IL)-2 and IL-12 and inversely with anti-inflammatory cytokines IL-1RA and IL-10.
Conclusions: In this referral cohort of children with severe juvenile myositis, metabolic abnormalities and predictors of cardiovascular disease were common, suggesting an increased risk of future cardiovascular disease. Indicators of insulin resistance correlated with muscle damage on magnetic resonance imaging and proinflammatory cytokines and inversely with anti-inflammatory cytokines.