Abstract
Limb girdle muscular dystrophy type 2I (LGMD2I) is an autosomal recessive muscular dystrophy that is rare in Asia and is caused by mutations in the fukutin-related protein gene (FKRP). The aim of this study was to determine if there are any characteristic features of muscle on magnetic resonance imaging (MRI) in patients with LGMD2I harboring the founder mutation c.545A>G in FKRP. Using MRI, we delineated changes in the thigh muscles of ten patients with genetically confirmed LGMD2I. The majority of muscle biopsy specimens showed reduced glycosylation of α-dystroglycan, decreased expression of laminin α2, and a dystrophic pattern. In our cohort, the muscles with the most severe fatty infiltration were adductor magnus and vastus intermedius, whereas the rectus femoris, sartorius, and gracilis muscles were relatively spared. In seven patients, we identified a concentric fatty infiltration pattern that was most pronounced in the vastus intermedius and vastus medialis muscles around the distal femoral diaphysis. In this disease, the initial fatty infiltration of the posterior thigh muscles gradually progresses anteriorly regardless of the founder mutation in FKRP. Muscle tissue in patients with LGMD2I who have the founder mutation c.545A>G in FKRP shows a distinctive concentric pattern of fatty infiltration and edema on MRI.
Highlights
Mutations in the fukutin-related protein gene (FKRP) have been shown to cause limb girdle muscular dystrophy type 2I (LGMD2I) [1, 2], which is common in Europe and North America but relatively rare in Asia
Several studies [3, 6, 11,12,13,14] have described the muscle magnetic resonance imaging (MRI) findings in European and North American patients with LGMD2I harboring the founder mutation c.826C>A in FKRP, which is different from the c.545A>G mutation found in mainland China [15]
We found no significant difference in disease severity between patients who were homozygous for the c.545A>G mutation and those with compound heterozygous mutations
Summary
Mutations in the fukutin-related protein gene (FKRP) have been shown to cause limb girdle muscular dystrophy type 2I (LGMD2I) [1, 2], which is common in Europe and North America but relatively rare in Asia. Several studies [3, 6, 11,12,13,14] have described the muscle MRI findings in European and North American patients with LGMD2I harboring the founder mutation c.826C>A in FKRP, which is different from the c.545A>G mutation found in mainland China [15]. Most of these studies [6, 11, 12, 14] suggest that there is initial fatty infiltration of the posterior thigh muscles with gradual progression anteriorly as the disease progresses. There have been some inconsistent findings in these studies, and the significance of muscle edema in LGMD2I
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