P.5.2 A comparison of muscle imaging in DYSF and ANO5 related muscular dystrophies

Abstract

In this descriptive retrospective and cross-sectional study we compared muscle images of patients with Miyoshi distal myopathy phenotype (MMD1 and MMD3) to limb girdle muscular dystrophy 2L (LGMD2L) patients. 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. A total of 35 muscle imaging studies of MMD1, MMD3 and LGMD2L patients was evaluated for fatty degeneration, muscle hypertrophy or atrophy and asymmetric muscle involvement. Eight muscle imaging scans of six MMD1 patients, 11 scans of nine MMD3 patients, and 16 scans of 14 LGMD2L patients were evaluated. Median disease duration was six years in MMD1, 13 years in MMD 3, and five years in LGMD2L. All groups showed predominant involvement of the gluteus minimus muscle and both the posterior segment of the thigh and calf muscles, with sparing of the gracilis muscle. The rectus femoris, anterior tibial, and extensor digitorum muscles were more frequently involved in MMD1 when compared with MMD3. The lateral head of the gastrocnemius muscle was more frequently involved in MMD3 in comparison to LGMD2L. Muscle hypertrophy or atrophy and asymmetric muscle involvement did not differ significantly between the groups. The pattern of fatty degeneration of muscles shows minor differences between MMD3 and MMD1 patients and is similar between the ANO5 related phenotypes. Therefore MMD3 and LGMD2L should be considered as part of one spectrum of ANO5 related muscle disease, equal to the dysferlinopathies, MMD1 and LGMD2B.