CAPN3 and limb-girdle muscular dystrophy: Calpain 3-related LGMD is the most common form of limb-girdle muscular dystrophy (LGMD) in most cases caused by biallelic variants in the calpain 3 gene (LGMD R1, CAPN3; equivalent to LGMD2A in the previous LGMD classification) [1, 2].