BACKGROUND: Duchenne muscular dystrophy (DMD) is a fatal progressive 
muscle-wasting disease caused by mutations in the DMD gene. Dilated 
cardiomyopathy is the leading cause of death in DMD; therefore, further 
understanding of this complication is essential to reduce morbidity and 
mortality.
METHODS: A common null variant (R577X) in the ACTN3 gene, which encodes 
α-actinin-3, has been studied in association with muscle function in healthy 
individuals; however it has not yet been examined in relationship to the cardiac 
phenotype in DMD. In this study, we determined the ACTN3 genotype in 163 
patients with DMD and examined the correlation between ACTN3 genotypes and 
echocardiographic findings in 77 of the 163 patients.
RESULTS: The genotypes 577RR(RR), 577RX(RX) and 577XX(XX) were identified in 13 
(17%), 44 (57%) and 20 (26%) of 77 patients, respectively. We estimated cardiac 
involvement-free survival rate analyses using Kaplan-Meier curves. Remarkably, 
the left ventricular dilation (> 55 mm)-free survival rate was significantly 
lower in patients with the XX null genotype (P < 0.01). The XX null genotype 
showed a higher risk for LV dilation (hazard ratio 9.04).
CONCLUSIONS: This study revealed that the ACTN3 XX null genotype was associated 
with a lower left ventricular dilation-free survival rate in patients with DMD. 
These results suggest that the ACTN3 genotype should be determined at the time 
of diagnosis of DMD to improve patients' cardiac outcomes.