Dystrophin and DNA Diagnosis in a Large Pediatric Muscle Clinic

Eighty-seven unrelated patients from a large muscle clinic setting were analyzed by DNA for deletions in the dystrophin gene for diagnosis of Duchenne/Becker muscular dystrophy. The clinical phenotype of the patient population included 72% Duchenne, 13% Becker, and 15% outlier patients. Dystrophin gene deletions were detected in 61% of these patients, and disease phenotype was predicted by DNA with an accuracy of 95%. While DNA did not confirm diagnosis in all patients, dystrophin analysis of muscle biopsies, when available, predicted a disease phenotype. In the 66 patients in which muscle biopsies were available for analysis, the results of the dystrophin analysis agreed with actual clinical phenotype with 86% accuracy. Less agreement between dystrophin and clinical phenotype predictions were found in the Becker patient population. We suggest that, in at least 61% of Duchenne/Becker patients, DNA analysis provides a rapid and accurate diagnosis. DNA is less invasive and less expensive than biopsy and may allow family risk assessment. Therefore, DNA analysis may become the first recommended laboratory procedure for Duchenne/Becker diagnosis, and muscle biopsy with dystrophin analysis may become necessary only for those patients with undetectable gene mutations.