CTSB and limb-girdle muscular dystrophy: Limb-girdle muscular dystrophy, LGMD, type 2A (calpainopathy) is one of the most common forms of LGMD worldwide and is caused by mutations in the CAPN3 gene, which encodes a skeletal muscle-specific Ca2+-activated nonlysosomal cysteine protease, CAPN3 (CAPN3) [1].