Open muscle biopsy in suspected myopathy: diagnostic yield and clinical utility

Background: The purpose of the study was to investigate the diagnostic yield and clinical utility of open muscle biopsy and to identify pre‐biopsy factors that might predict useful clinical results for suspected myopathy. Methods: Two‐hundred fifty‐eight muscle biopsies, performed for investigation of suspected myopathy, were evaluated. Results: A specific clinical diagnosis following muscle biopsy was made in 43% of cases. As a result of the biopsy, clinical diagnosis was changed in 47% and treatment was changed in 33% of cases. Results either led to a specific clinical diagnosis or changed the diagnosis/treatment in 74% of patients. Positive family history of myopathy and findings of myopathic irritability on electromyography had a negative predictive value for diagnosis change. Conclusions: Open muscle biopsy is useful in myopathy evaluation in the modern genetic era.