Muscle imaging in patients with central core disease (CCD) caused by mutations in the ryanodine receptor 1 gene (RYR1) shows a characteristic pattern with main involvement of the gluteus maximus in the pelvis. At the thigh level, the most severe changes are observed in the medial compartment (adductor magnus) and in the anterior compartment muscles (vastus lateralis, vastus intermedius). Sparing of the adductor longus, gracilis and biceps femoris muscles is common. In the distal lower leg muscles, the soleus and the lateral head of the gastrocnemius muscles are most severely involved [61, 62]. This pattern seems to be highly characteristic, as muscular involvement in other congenital myopathies caused by mutations in the SEPN1, ACTA1, NEB or collagen VI encoding (COL6A1, COL6A2 and COL6A3) genes is different [1]. In addition to RYR1, patients with Ullrich CMD or Bethlem myopathy related to collagen VI encoding genes also present with dominant affliction of the anterior thigh compartment. These patients show an early and selective involvement of the centre of the rectus femoris and vastus lateralis muscles. In addition, in the lower legs there is often a rim of degenerative changes between the soleus and the gastrocnemius muscle, a pattern not observed in other CMs [63, 64].