Predictive role of muscle MRI in juvenile dermatomyositis: A tertiary center experience

To investigate muscle MRI findings in juvenile dermatomyositis (JDM) and assess their relationship with clinical parameters and myositis-specific autoantibody (MSA) profile.

59 MRI scans from 42 cases with JDM were analyzed retrospectively. Distribution and pattern of myositis, symmetricity, fascial and/or subcutaneous involvement, and presence of calcinosis, were evaluated. Clinical features, serum creatine kinase (CK) levels, and MSA profile were recorded.

Myositis was detected in 71.4 % of cases (n = 30), with 8/30 (26.6 %) being clinically inactive at the time of MRI. The most common dominant distribution and pattern types of myositis were diffuse (n = 15; 50 %) and foggy (n = 21; 70 %), respectively. Fascial and subcutaneous involvement were observed in 86.7 % and 73.3 % of cases and were significantly associated with the presence of calcinosis (p = 0.016 and 0.004, respectively). The dominant pattern of myositis was significantly associated with MSA profile, with the honeycomb pattern being more frequent in MSA-negative cases, and the foggy pattern in MSA-positive cases (p = 0.029 and 0.04, respectively). No significant associations were found between MRI findings and clinical features or serum CK levels.

Muscle MRI is a valuable tool for detecting subclinical disease activity in JDM, suggesting that disease activity and qualitative MRI findings may not always align with each other. Fascial and subcutaneous involvement were associated with the presence of calcinosis, suggesting a potential role of MRI in identifying cases at risk for developing calcinosis. Of note, the presence of foggy pattern on MRI was associated with the presence of MSAs.