These myopathies are due to mutations in several genes, including dystrophin (Duchenne muscular dystrophy, DMD), calpain-3 (Limb girdle muscular dystrophies, LGMD2A), or titin [muscular dystrophy with myositis (MDM); tibial muscular dystrophy (TMD) and limb-girdle muscular dystrophy 2J (LGMD2J)] (Hackman et al., 2002; Huebsch et al., 2005; Udd et al., 2005). The gene discussed is TTN; the disease is tibial muscular dystrophy.