Muscle MRI in Ullrich congenital muscular dystrophy and Bethlem myopathy

The aim of this study was to evaluate the spectrum of muscle involvement on Magnetic Resonance Imaging (MRI) in patients with collagen VI related disorders. Nineteen patients with genetically confirmed collagen VI related disorders, 10 with Bethlem myopathy and 9 with Ullrich congenital muscular dystrophy (CMD), had muscle MRI of their legs using T1 sequences through calves and thighs. In patients with Bethlem myopathy the vasti muscles appeared to be the most frequently and most strikingly affected thigh muscles, with a rim of abnormal signal at the periphery of each muscle and relative sparing of the central part. Another frequent finding was the presence of a peculiar involvement of the rectus femoris with a central area of abnormal signal within the muscle. Patients with Ullrich CMD had a more diffuse involvement of the thigh muscles with relative sparing of sartorius, gracilis and adductor longus. In 8 of the 9 patients with Ullrich CMD, we also observed the peripheral rim of the vastus lateralis and the central area in the rectus femoris observed in patients with Bethlem myopathy. At calf level the results were more variable but a significant proportion of patients with both Bethlem myopathy (8/10) and Ullrich CMD (6/9) showed a rim of abnormal signal at the periphery of soleus and gastrocnemii. Bethlem myopathy and Ullrich CMD patients have distinct patterns of muscle involvement on MRI with some overlap between the two forms. Our results suggest that muscle MR may be used, as an additional tool, to identify patients with collagen VI related disorders. This information is even more important in the patients with a typical Ullrich CMD clinical phenotype but with normal collagen expression of VI in muscle and/or skin.