Deletion and duplication mutations spectrum in Duchenne muscular dystrophy in the southwest of Iran

Background: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked disorders caused by the mutation within the dystrophin gene. Objectives: the primary objective of this study was to evaluate the deletion and duplication mutations in DMD patients. Materials and methods: Our study has identified 33 Iranian patients collected from Narges Genetic lab, southwest of Iran, Ahvaz. All cases were subjected to complete clinical evaluation pedigree analysis, electromyography studies, estimation of serum creatine phosphokinase (CPK) level, and DNA analysis. DNA samples were analyzed by multiplex-ligation-dependent probe amplification (MLPA). Results: In this study, deletion rate was 75% (25/33) and more frequent in the distal end exons whereas duplication rate was 25% (8/33) and it is more frequent at proximal exons. Most of the deletion (15/25, 60%) were located on the distal hot spot region (exon 44-55). Majority of exon duplications 62.5% (5/8) were located at the proximal hot spot region (exon 1-16) and 37.5% (3/8) were located at the distal hot spot region (exon 50-62). Single exon deletions were present in 10/25 patients (40%) which are mostly were in exon 45, 51 and 52 with similar frequencies (2/25, 8% each). One patient had a de novo single exon deletion (exon 51) and whole dystrophin gene was deleted in only one patient. Conclusion: This finding indicates that as with deletions, duplications occur non-randomly but with a dramatically different distribution. Duplication frequency is highest near the 5' end of the gene.