Clinical significance of subcutaneous fat and fascial involvement in juvenile dermatomyositis

Objectives: Subcutaneous involvement, including calcinosis and panniculitis, is a more common complication in juvenile dermatomyositis (JDM) than in adult dermatomyositis. Magnetic resonance imaging (MRI) is useful for evaluating disease distribution. We investigated the clinical significance of subcutaneous involvement in JDM. Methods: Thighs and hips in 18 newly diagnosed JDM patients were evaluated with fat-suppression MRI. Bilateral muscle, fascial and subcutaneous fat involvement were scored from 0 to 8 points according to the severity of distribution on MRI. Associations between clinical manifestations, serum muscle enzymes, and MRI scores were also evaluated. Results: Abnormal MRI findings in muscle, fascia and subcutaneous fat were observed in 18, 18, and 10 patients, respectively. Subcutaneous fat scores were significantly higher in early-diagnosed JDM patients (diagnosed less than 2 months from onset) than in late-diagnosed JDM patients (diagnosed later) (p = .025). Serum aldolase was elevated in all patients, although only eight demonstrated elevated serum creatine phosphokinase. Serum aldolase was significantly correlated with MRI scores for subcutaneous fat (p < .0001, ρ = .787) and fascia (p = .013 ρ = 0.574), but not muscle. Additionally, serum aldolase was significantly correlated with serum triglycerides (p = .009, ρ = 0.629). Conclusion: Subcutaneous fat involvement is a characteristic finding in early-diagnosed JDM and correlates with elevated serum aldolase.