Abstract
AIMS: This study was designed to evaluate the magnetic resonance imaging (MRI) patterns of the lower limb muscles in dermatomyositis (DM) with anti-transcriptional intermediate factor 1-γ (anti-TIF1-γ) antibody. METHODS: This retrospective, observational, cross-sectional study enrolled 12 adult DM patients with anti-TIF1-γ antibody. Muscles were assessed for fascial edema, subcutaneous-tissue edema, muscle edema, and fatty replacement. These features were analyzed in relation to clinical characteristics. RESULTS: All 12 patients underwent hip and thigh MRI, and 8 completed calf MRI. All patients showed myofascial edema, muscle edema, and fatty replacement, and 8 out of 12 further exhibited subcutaneous-tissue edema. Specifically, myofascial edema of the gastrocnemius was observed in all patients (8/8). The vastus intermedialis and vastus lateralis muscles showed the most severe muscle edema, whereas the caput breve of the biceps femoris, semitendinosus, and soleus muscles exhibited the most severe fatty replacement. Although only 1 patient exhibited asymmetric muscle weakness, 9 showed asymmetric muscle edema, and 10 showed asymmetric fatty replacement. Changes in muscle edema positively correlated with creatine kinase (CK) levels. CONCLUSIONS: Myofascial edema of gastrocnemius was a prominent characteristic of anti-TIF1-γ-positive DM. Early detection of muscle edema, as well as CK levels, may be helpful for monitoring disease activity.