Magnetic resonance imaging changes of thigh muscles in dermatomyositis patients with anti-Mi2 antibody

BACKGROUND: Anti-complex nucleosomal remodelling histone deacetylase (Mi2)-positive dermatomyositis (DM) is characterized by severe muscle damage. This study investigated muscle magnetic resonance imaging (MRI) features in anti-Mi2-positive DM, compared them with other DM subtypes, and evaluated their associations with clinical features. METHODS: DM patients who underwent thigh MRI were enrolled, including 20 anti-Mi2-positive, 20 anti-TIF1γ-positive, 15 anti-NXP2-positive, and 19 anti-MDA5-positive cases. Clinical and imaging data were collected and compared across subtypes. The relationship between MRI features and clinical characteristics was analysed in the anti-Mi2-positive subgroup. RESULTS: < 0.05). Preliminary observations in six anti-Mi2-positive patients followed longitudinally showed that muscle oedema decreased after treatment, resolved during remission, and recurred with relapse. CONCLUSION: This study delineated baseline thigh MRI patterns in anti-Mi2-positive DM and demonstrated that baseline muscle oedema severity correlated with serological and clinical indicators of muscle damage. Additionally, findings from a small longitudinal cohort suggested a potential role for thigh MRI in assessing and monitoring muscle disease activity in this subtype, although these results are preliminary and require validation in larger studies.