Background: Limb-girdle muscular dystrophy 2E (LGMD 2E), recently renamed as autosomal recessive limb-girdle muscular dystrophy-4 (LGMDR4), is characterized by the lack of beta-sarcoglycan, normally expressed in skeletal muscles and cardiomyocytes.

At the link https://pubmed.ncbi.nlm.nih.gov/34276533/ you can read the complete article on the natural history study of GFB with the title "clinical determinants of disease progression in patients with beta-sarcoglycan gene mutations"