Prognosis in patients with Duchenne muscular dystrophy (DMD) is guarded and most deaths are due to cardiac or respiratory causes. It is unclear if some DMD gene mutations might be predictive of either mild or severe cardiac dysfunction. We studied 75 patients with DMD followed at our institution. Cardiac function, as assessed by yearly echocardiography, showed marked variability in left ventricular (LV) function. Some patients in their 3rd decade had no or minimal dysfunction whereas others in their 2nd decade had very severe dysfunction. Therefore, 4 Severity Groups were defined ranging from no/mild LV dysfunction to severe LV dysfunction using patient age at first abnormal echocardiogram and degree of LV dysfunction. Genetic data were collected for all patients. The majority of patients had mutations between exon 1 – 20 and exon 41 – 55. The distribution of the 4 Severity Groups of LV dysfunction did not significantly differ among these two mutation groups. An analysis based on the number of exons involved (< 5 exons versus ≥ 5 exons) also found no significant difference in cardiac severity. When patients having identical mutations were compared as to their cardiac course, concordance was often not evident. Steroid therapy had no apparent protection for the development of cardiomyopathy. In conclusion, 75 patients with DMD showed marked variability in the severity of LV dysfunction. Neither age of onset nor severity of cardiomyopathy correlated with any of the mutation groups.
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