Fig. 5 Muscle imaging differences in myofibrillar myopathies. Highly specific and sensitive statistical criteria were identified in a systematic retrospective muscle imaging assessment in a large series of 43 MFM patients [24]. Equal or greater affliction of the semitendinosus than the biceps femoris and equal or greater affliction of the peroneal group than the tibial anterior muscles is highly specific for primary desminopathy and crystallinopathy (18 out of 19 patients). Those of the remaining patients who had equal or greater involvement of the sartorius than the semi-tendinosus and equal or greater involvement of the adductor magnus than the gracilis usually had a myotilin mutation (eight out of nine patients). All eight patients who did not fulfil the criteria for desmin and myotilin mutations and who had more involvement of the medial than the lateral gastrocnemius showed a filamin C mutation. Two of the three remaining patients had a ZASP and the third a myotilin mutation