Trial Readiness and Endpoint Assessment in LGMD R1

This is a 24-month, observational study of 100 participants with Limb Girdle Muscular Dystrophy type R1, also known as CAPN3.

Inclusion Criteria:Age between 12-50 at enrollmentClinically affected (defined as weakness on bedside evaluation in a pattern consistent with LGMDR1)Genetic confirmation of LGMDR1 (presence of homozygous or compound heterozygous pathogenic mutations in CAPN3).Exclusion Criteria:Have contraindications to MRI or MRS (e.g., non-MR compatible implanted medical devices or severe claustrophobia)Non-ambulatory as defined by those who are not able to walk 10 meters without assistive devices (AFOs excluded)Any other illness that would interfere with the ability to undergo safe testing or would interfere with interpretation of the results in the opinion of the site investigator.