A novel nonsense mutation in the dimerization domain of FLNC causing mild myofibrillar myopathy.

Skeletal muscle filaminopathy is caused by mutations in the gene encoding filamin C (FLNC). The phenotypes include both proximal and distal myopathy, of which proximal myopathy phenotype pathologically displays myofibrillar myopathy as mutated filamin C produces protein aggregates. FLNC-related myofibrillar myopathy usually starts in the fourth to fifth decade and often progresses to cause inability to walk, respiratory muscle weakness requiring nocturnal ventilation, and cardiac abnormalities, such as conduction blocks and diastolic dysfunction. We report a 65-year-old patient with myofibrillar myopathy caused by a novel heterozygous nonsense mutation in the dimerization domain of FLNC, in whom histopathological features were highlighted by histological and immunohistochemical studies. The reported patient showed slow progression of mild limb weakness since her childhood.