Dystrophinopathy muscle biopsies in the genetic testing ERA: One center's data

: Comprehensive genetic testing for dystrophinopathy can detect ∼95% of pathogenic variants in the dystrophin gene ( DMD ) and is often the preferred diagnostic approach. Methods : We reviewed pathology reports for muscle biopsies evaluated at the University of Iowa with a pathological diagnosis of dystrophinopathy based on dystrophic histopathology and abnormal immunofluorescence staining: reduced to absent dystrophin, expression of utrophin, and loss of neuronal nitric oxide synthase. Results : The percentage of muscle biopsies with dystrophinopathy has been stable since 1997. Among 2,298 biopsies evaluated between 2011 and 2016, 72 (3.1%) had pathologic features of dystrophinopathy. Median age at biopsy was 8 years (range, 0.66–84). Half had undergone DMD genetic testing prior to biopsy. Clinical phenotypes recorded on requisitions were typical of muscular dystrophy for 57 (79%) biopsies. Discussion : Muscle biopsy continues to play an important role in the diagnosis of dystrophinopathy, particularly in patients with later symptom onset, comorbidities, or normal DMD genetic testing results. Muscle Nerve 58 : 148–152, 2018