Serial case report: Becker’s muscular dystrophy phenotype with dilated cardiomyopathy in patients with out-of-frame deletion involving exons 38-43 of DMD gene

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive allelic muscular dystrophies due to mutations of the DMD gene, showing more severe and milder phenotype, respectively. Here we present, two brothers, ages 23 years old (case 1) and 19 years old (case 2) who presented with clinical symptoms typically associated with BMD, including dilated cardiomyopathy in the first case and mild cardiac enlargement in the second. Muscle symptoms were moderate enabling independent ambulation of both patients until the present. Dystrophin protein was patchy on immunohistochemistry staining confirming the diagnosis of BMD. However, genetic analysis using Multiple Ligation-dependent Probe Amplification (MLPA) identified out-of-frame deletions involving exons 38-43 of the DMD gene in both cases. Here, we report a case series with an exception to the reading frame rule due to mutations affecting the central rod domain of the DMD gene.