CTSB and autosomal recessive limb-girdle muscular dystrophy type 2A: Limb-girdle muscular dystrophy type 2A (LGMD2A) is a neuromuscular disease caused bymutations in the gene encoding calpain 3 (CAPN3), a nonlysosomal cysteine protease necessaryfor normal muscle function and regeneration (Refs 1,2).