A different spectrum of DMD gene mutations in local Chinese patients with Duchenne/Becker muscular dystrophy

Background Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive, allelic disorders. This study was conducted to look into the spectrum of DMD gene mutations in Hong Kong Chinese patients with Duchenne or Becker muscular dystrophy (DMD/BMD), and to study genotype-phenotype correlation. Methods A retrospective review of 67 patients. Results Twenty-three (34.3%) patients had exon deletions; whereas 5 (7.5%) patients had exon duplications. Twenty-three (34.3%) patients had small mutations, including 17 point mutations and 6 small insertions or deletions. No correlation was found between the type of mutation and the muscle phenotype or mental retardation. Significantly fewer maternal carriers were found in patients with exon deletions, and a positive fan-Lily history was more common in those with small mutations. DMD phenotype was significantly less common in patients with exon deletions/duplications at the 5' hotspot, whereas all 4 small mutations associated with mental retardation were located in the 3' end of the gene. Conclusions The percentage of DMD exon deletions in local Chinese patients was significantly lower than the commonly quoted 60%. This indicated an ethnic or regional difference in predisposition to DMD exon deletions.