Imaging Features of Skeletal Muscle and Their Correlation With Clinical Findings in Emery-Dreifuss Muscular Dystrophy...

Variants in the EMD gene cause Emery-Dreifuss muscular dystrophy type 1 (EDMD1). While the pattern of fat replacement in the legs of patients with EDMD1 is known, the involvement of the trunk and arms remains unclear. This study aimed to characterize the whole-body distribution of fatty replacement in EDMD1 and clarify its relationship with clinical symptoms.

Imaging data from eight Japanese EDMD1 patients was analyzed. Fatty replacement in 47 skeletal muscles was scored using the modified Mercuri score (mMS). Hierarchical clustering classified patients according to mMS, and intercluster differences were assessed.

Fatty replacement was observed in the soleus and paraspinal muscles in all patients, as well as in the medial gastrocnemius, semimembranosus (Sm), biceps femoris long head (BFL), serratus anterior (SA), and biceps brachii (BB) in seven patients. A significant difference in mMS was observed between the low- and high-score groups in the SA (p = 0.0042), BB (p = 0.0031), semitendinosus (p = 0.0015), Sm (p < 0.0005), and BFL (p = 0.0031). Elbow flexion strength on manual muscle testing strongly correlated with BB mMS (p = 0.03, r = -0.75). The patient with a missense variant had a lower mMS than those with truncating variants.

Elbow flexion strength is a potential marker of disease severity. The finding that the patient with a missense variant had a lower mMS supports previous reports that missense variants are associated with milder phenotypes. Genetic variant type should be considered in biomarker development for EDMD1.