Magnetic resonance imaging detection of occult skin and subcutaneous abnormalities in juvenile dermatomyositis - Implications for diagnosis and therapy

Objective. To assess the utility of magnetic resonance imaging (MRI) of ski n, subcutaneous tissue, and fascia in evaluating disease activity in juveni le dermatomyositis (DM). Methods. Short tau inversion recovery (STIR) MRI of the proximal thighs and buttocks, cutaneous assessment, and other measures of disease activity wer e prospectively obtained in 26 children meeting criteria for probable or de finite juvenile DM. Also undergoing STIR MRI assessment were 8 subjects who were being evaluated for muscle disorders and who were not diagnosed as ha ving juvenile DM. Results. Skin, subcutaneous, or fascial edema of the thighs and buttocks we re seen on STIR MRI in up to 85% of juvenile DM patients at baseline evalua tion compared with no more than 38% of the comparison group without juvenil e DM. In juvenile DM, STIR MRI skin and subcutaneous edema scores correlate d (r(s) = 0.51, P = 0.008), as did fascial and muscle edema scores (r(s) = 0.58, P = 0.002). Skin global disease activity scores correlated with MRI s kin edema scores (r(s) = 0.41, P = 0.04), and serum aldolase levels correla ted with both MRI skin and subcutaneous edema scores (r = 0.44 and 0.40, P = 0.03 and 0.05 respectively). The extent and severity of STIR MRI changes in the skin, subcutaneous tissue, and fascia were not predicted by most oth er measures of juvenile DM disease activity. Five juvenile DM patients with thigh MRI subcutaneous edema developed clinically apparent calcinosis at t he same location within 9 months. Conclusion. Edema or inflammation in the skin, subcutaneous tissue, and fas cia, found on STIR MRI, is common in juvenile DM patients and is often unde tected by standard assessments. These MRI changes can precede the developme nt of calcinosis. STIR MRI may be a useful adjunct for assessing disease ac tivity and guiding the treatment of juvenile DM.