Myofibrillar myopathy (MFM) encompasses a genetically and clinically heterogeneous group of
inherited or sporadic skeletal muscle disorders characterized pathologically by the presence of myofibrillar
dissolution associated with accumulation of myofibrillar degradation products and ectopic expression of
multiple proteins especially Z-disk related proteins. Patients with MFM initially present with muscle weakness
and commonly developed cardiomypathy in the advanced stage. To date, mutations of genes encoding Z-disk
proteins or proteins maintaining myofibrillar integrity including ZASP, MYOT, DES, FLNC and CRYAB underlie
MFM. The authors herein report a 29-year-old Thai woman with a clinical diagnosis of autosomal dominant
limb-girdle muscular dystrophy (LGMD1) who has one affected grandmother. The patient was subsequently
found to have MFM based on her myopathological findings. Analyses of all MFM-genes known to date
revealed no mutations. The current case emphasizes the importance of muscle biopsy in LGMD1 patients and
a wide range of phenotypic variations among patients with MFM. The causative genes underlying the majority
of MFM remain uncovered. Close monitoring of the cardiac function is crucial to prevent mortality among
these patients.

Keywords: αB-crystallin, Desmin, Filamin C, Limb-girdle muscular dystrophy, LGMD, Myofibrillar myopathy,
Myotilin, ZASP