Fig. 4

Muscle MRI of lower limb of three cases with different severity. Upper images refer to thigh, whereas lower images refer to calf muscles. Case 7 in (a) is the less affected and only initial fat substitution of tibialis anterior is noted. This feature is shared by all the patients. Interesting, in this case only, the tibialis involvement seems to start from the periphery of the muscle, a feature which has been already described in quadriceps muscles of COL6 mutated patients. In (b) involvement of medial gastrocnemius and very initial involvement of vastus medialis is present. This MRI belongs to case 6 at age 16. In (c) the tibialis anterior is totally replaced by fat tissue. Medial and lateral gastrocnemii are also affected. In the thight, vastus medialis and adductor magnus are involved but rectus femori is spared. This is case 5 and MRI was performed at 44 years of age