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Genetic testing of muscle diseases has moved to the forefront of diagnostic investigation replacing the use of muscle biopsy in many instances. 

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Our patient is a 27 year old female, referred to us with slowly progressive proximal lower extremity weakness.  In addition to weakness in her hip flexors and adductors, she was noted to have calf atrophy and weakness. Her mother and brother had complaints of muscle weakness. CK was markedly elevated, 5485 U/L. EMG findings showed features of an irritable myopathy. Dysferlinopathy was suspected, based on the phenotype and CK. A myopathy gene panel showed variant of uncertain significance (VUS) in the dysferlin gene (Homozygous C4519A to C) and a VUS in LAMA2 gene (Heterozygous, C7055G to C, associated with AR LAMA 2 related myopathy). Muscle biopsy demonstrated myofiber segmental necrosis, split fibers, upregulation of C5b9 with limited to no significant inflammation, complete loss of dysferlin expression, and retained merosin (laminin-a2) expression, consistent with the clinical suspicion for dysferlinopathy. The patient was managed through multidisciplinary approach with cardiac evaluation, pulmonary evaluation and physical therapy. 

The muscle biopsy is still a valuable but often less commonly used tool in the era of readily available genetic testing especially in cases of novel genetic mutations.