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

内容摘要

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. DM patients who underwent thigh MRI were enrolled, including 20 anti-Mi2-positive, 20 anti-TIF1&#x3b3;-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. Among the four subtypes, anti-Mi2-positive DM had the highest myofascial oedema frequency in the sartorius and the lowest in the biceps femoris (both p&#x202f;<&#x202f;0.05). All anti-Mi2-positive patients had muscle oedema - most severe in the quadriceps femoris with relative sparing of the semimembranosus and biceps femoris - and the highest total muscle oedema scores (p&#x202f;<&#x202f;0.001). Eleven (55%) patients had fatty infiltration, predominantly in the gluteus maximus and hamstrings with sparing of the rectus femoris and adductor longus. In this subgroup, treatment-na&#xef;ve patients had a higher prevalence of diffuse distribution than treatment-experienced (p&#x202f;=&#x202f;0.042). Compared with anti-TIF1&#x3b3;-positive patients, the anti-Mi2-positive subgroup had lower total fatty infiltration scores and milder gluteus maximus, adductor longus, and hamstrings involvement (all p&#x202f;<&#x202f;0.05). In anti-Mi2-positive DM, total muscle oedema scores correlated negatively with Manual Muscle Testing-8 scores and positively with serum creatine kinase levels (both p&#x202f;<&#x202f;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. 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. Our findings identified baseline patterns of oedema and fatty infiltration on thigh muscle MRI in patients with anti-Mi2-positive DM, with oedema being more pronounced and asymmetric than fatty infiltration.Among the four subtypes, anti-Mi2-positive DM showed the highest frequency of myofascial oedema in the sartorius and the lowest in the biceps femoris; it also exhibited the most severe muscle oedema.This study demonstrated that baseline muscle oedema severity correlated with serological and clinical indicators of muscle damage, and 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.