DYSF and muscular dystrophy: Dysferlinopathy is a term for a group of rare muscular dystrophies with recessive mutations in the DYSF gene, which encodes the skeletal muscle protein dysferlin.1,2 Two major phenotypes are Miyoshi myopathy (MM),3 presenting with distal weakness and limb-girdle muscular dystrophy type 2B (LGMD2B),4,5 affecting more proximal muscles.