Rationale: Although several studies have described the involvement pattern of myotonic dystrophy type 1 (DM1) using muscle MRI, most of these studies have limitations as cross-sectional studies. To the best of our knowledge, there have been no reports of longitudinal studies describing muscle involvement patterns in patients with DM1 via serial MRI.
Patient concerns: Progressive weakness of both lower extremities.
Diagnosis: Two patients with DM1.
Intervention: The serial muscle MRI performed in the 2 patients with DM1.
Outcomes: The serial muscle MRI showed early involvement of proximal (tensor fascia latae) and truncal muscles (spine extensor muscles), and these longitudinal imaging may be helpful to reveal the pattern of muscle involvement in patients with DM1.
Lessons: Since most previous studies on muscle involvement patterns in DM1 patients were cross-sectional studies, this case series of studying muscle involvement patterns through serial MRI in patients with DM1 may have significant clinical significance.