Figure 4.

Muscle MRI patterns. Axial T1-weighted images at mid-thigh and mid-calf level in selected subjects. (A–C) Patients with genetically confirmed MYOT mutations all correctly identified. They are all characterized by a relative sparing of the semitendinosus (ST) muscle. The vastus intermedius and sartorius muscles are more affected than the gracilis muscle. All calf muscles can be affected; the gastrocnemius lateralis muscle is usually less affected than the medialis. (D) Patient with TTN (ID18) mutation. He was not correctly identified as the calf was severely involved without the characteristic pattern. However the selective involvement of semitendinosus (ST) within the thigh is characteristic and could represent a key feature of this disease. (E,F) Patients with GNE mutations. One patient (E, ID11) was not correctly identified. The rectus femoris muscles were spared and the vastus lateralis muscles were involved contrary to the reported pattern. However both patients (E,F) revealed severe involvement of short head of biceps femoris (SB) muscles which could represent a key feature of the disease.