Descrição
Mutations in the dystrophin gene (DMD) give rise to the allelic Duchenne or Becker muscular dystrophies. Besides providing a differential diagnosis for adequate clinical follow-up and management, the molecular characterization of these patients is becoming increasingly important in light of the recent and promising mutation-based therapeutic approaches. Due to the size and complexity of DMD, as well as the diversity of mutation types, molecular analysis requires a combination of techniques that enable the detection of gross deletions, duplications and the more subtle point mutations. In the course of our diagnostic service provided on a national basis, a total of 307 patients, representing 282 unrelated families, have been characterized at the molecular level. We identified 174 different mutations, where the distribution according to type was found to be in agreement with that reported in the literature for large cohorts. Also as expected, approximately 1/3 of the cases were shown to be de novo occurrences, as ascertained among the “sporadic” cases (25/82). These neo-mutations were comprised by 18% deletions, 6% duplications and 6% point mutations. We describe a total of thirty-nine undocumented variants, three of which were detected in obligate carrier female relatives of deceased patients. These new variants include 9 gross deletions, 8 gross duplications and 22 smaller mutations (deletions, duplications, delins rearrangements and nonsense or splice-site substitutions). Comprehensive analysis often involved expression studies at the mRNA level to help delineate breakpoint junctions, to identify altered splicing and ultimately to provide an explanation for apparent exceptions to the reading frame rule. This detailed molecular characterization is also important for the purpose of including our patients in the DMD National Registry, which will be articulated with the TREAT-NMD Global Database
; Santos, Rosário 
