Gene Mutation Spectrum Analysis of 170 Patients with Duchenne/Bayesian Muscular Dystrophy inSouthwest of China

Objective To determine gene variations and genotype-phenotype correlations in Duchenne/Bayesian muscular mystrophy (DMD/BMD) patients, and the association between dystrophin gene polymorphisms and clinical phenotype. Methods Multiplex ligation-dependent probe amplification (MLPA) was adopted to detect dystrophin gene variations in 170 patients. Sanger sequencing was performed in 3 cases with decreased peaks in MLPA results. Results The MLPA detected 72.94% mutations in dystrophin gene, including 62.35% (106/170) deletions, 8.82% (15/170) duplications, and 1.76% (3/170) point mutations. 64 different types of mutations were found. 75.47% of deletions occurred in the range from exon 44 to 55. Most 5’ breakpoints of exonic variations were located in 2 hotspots (major hotspot: intron 43-55; minor hotspot: intron 1-20), which is different from findings of other studies. Genotype-phenotype analysis showed that the severity of DMD/BMD was associated with frame shift mutation ( r =0.640, P<0.001) but not with deletions or duplications. Conclusion Deletions and duplications of exon compose the main type of dystrophin gene mutations. DMD/BMD is associated with frame shift mutation.