Comparing clinical data and muscle imaging of DYSF and ANO5 related muscular dystrophies

In this retrospective cross-sectional study clinical and muscle imaging data of patients with Miyoshi distal myopathy phenotype (MMD1 and MMD3) and limb girdle muscular dystrophy 2L (LGMD2L) were described. MMD1 and MMD3 are genetically heterogenous diseases based on DYSF and ANO5 gene defects. MMD3 and LGMD2L are clinically different diseases caused by an ANO5 gene defect. All groups showed predominant fatty degeneration of the gluteus minimus muscle and of the posterior segments of the thigh and calf muscles with sparing of the gracilis muscle. Muscle atrophy, hypertrophy and asymmetric muscle involvement on muscle imaging did not differ between groups. The pattern of fatty degeneration of muscles and of muscle weakness shows only minor differences between MMD1 (n=6) and MMD3 (n=8) patients with more frequently fatty degeneration of the rectus femoris, anterior tibial, and extensor digitorum muscles and more frequently muscle weakness in the anterior tibial, peroneal and calf muscle in MMD1. In the ANO5 related phenotypes the lateral head of the gastrocnemius muscle was less frequently involved in LGMD2L (n=13) and no differences in the incidence of muscle weakness was found. Therefore, MMD3 and LGMD2L should be considered as part of one spectrum of ANO5 related muscle disease.