Sarcopenia in juvenile localized scleroderma: new insights on deep involvement

Objectives Juvenile localized scleroderma (JLS) is a rare chronic autoimmune disease which can also affect bones and muscles. Nevertheless, muscle loss was not previously investigated in patients with JLS. Thus, the aim of this study was to retrospectively evaluate deep involvement and assess and quantify sarcopenia in JLS patients using magnetic resonance imaging (MRI). Methods Fourteen children with JLS (nine females, mean age +/- SD, 7.1 +/- 3.6 years) referring to our tertiary center from January 2012 to January 2018 who underwent at least one MRI examination including axial T1-weighted and short tau inversion recovery images were included. Two readers assessed in consensus superficial and deep involvement. Muscle edema, muscle fatty infiltration, and sarcopenia were independently scored (absent, moderate, or severe) and the Cohen's kappa coefficient computed. Skin perimeter, subcutaneous area, muscle area, and muscle volume were independently measured using the contralateral unaffected extremity as reference (paired Student'sttest,p < 0.05). The intraclass correlation coefficient (ICC) was used to investigate the reliability of the measurements. Results All patients showed superficial involvement with subcutaneous fat atrophy being the most common finding (13 patients). Bone marrow edema occurred in five patients. Muscle edema affected ten children (moderate in seven, severe in three;k = 0.89), muscle fatty replacement occurred in one case (severe;k = 1.00), and sarcopenia was detected in eight patients (severe in two;k = 0.78). All quantitative parameters were lower on the affected side than on the unaffected contralateral limb (p < 0.05, each) and all measurements showed a high reliability (ICC > 0.750, each). Conclusion Patients with JLS can be affected by sarcopenia and quantitative analyses allow a robust characterization of such finding.