MYOT and myofibrillar myopathy 3: However, despite the fact that mutations in the myotilin gene have been implicated in limb girdle muscular dystrophy 1A (LGMD1A) [51], myofibrillar myopathy (MFM) [52], and in a rare condition called spheroid body myopathy (SBM) [53], the function of myotilin in normal muscle physiology remains unclear.