The overall goal of this natural history study is to define the key LGMD2i phenotypes as measured by standard clinical outcome assessments (COAs), and to validate a muscle biomarker for LGMD2i to support therapeutic development.
Limb Girdle Muscular Dystrophy (LGMD) 2i is an autosomal recessive form of LGMD that is due to missense mutations in the Fukutin-related protein (FKRP) gene. Patients develop progressive proximal muscle weakness that leads to loss of ambulation. Patients will also commonly develop a cardiomyopathy and respiratory compromise. There are promising new therapies that have been developed and as a result therapeutic trials are approaching. The rationale for this study is to define appropriate COAs for LGMD2i, which will facilitate therapeutic development and ensure properly powered clinical trials. In addition, measurement of dystroglycan in muscles represents a potential muscle biomarker that could be used in early phase clinical trials as a measure of target engagement. The clinical utility of changes in dystroglycan has not been validated in human samples.