Park D, et al. – Correlations among clinical, genetic, and magnetic resonance imaging (MRI) data of muscles in myotonic dystrophy type 1 (DM1) were explained in this study. The most severely affected muscles revealed in the whole body MRI were the ankle plantar–flexor muscles and presented statistically significant correlation with the six–minute walk test results (6MWT). The soleus muscle most influenced the 6MWT among the plantar–flexor muscles.

• The medical records and images of 19 patients with DM1 from different families were retrospectively reviewed.
• The authors retrieved the genetic data (CTG repeats) and the clinical data, which included disease duration, creatine kinase level, the sum score of manual muscle testing, modified Medical Research Council sum score (modified MRCSS), and the six-minute walk test results (6MWT).

• The authors demonstrated a statistically significant association between the modified MRCSS and CTG repeat numbers in the correlation analyses.
• 6MWT correlated most with the sum of the ankle plantar-flexors among the lower extremity muscles (the soleus, medial, and lateral gastrocnemius muscles).
• The soleus muscle presented the highest correlation with the 6MWT than the other plantar-flexor muscles.
• Furthermore, the outcomes demonstrated that the CTG repeat numbers did not correlate with the 6MWT, however, it correlated with the modified MRCSS.