Creatine kinase has been utilized as a diagnostic marker for Duchenne muscular 
dystrophy (DMD), but it correlates less well with the DMD pathological 
progression. In this study, we hypothesized that muscle-specific microRNAs 
(miR-1, -133, and -206) in serum may be useful for monitoring the DMD 
pathological progression, and explored the possibility of these miRNAs as 
potential non-invasive biomarkers for the disease. By using real-time 
quantitative reverse transcription-polymerase chain reaction in a randomized and 
controlled trial, we detected that miR-1, -133, and -206 were significantly 
over-expressed in the serum of 39 children with DMD (up to 3.20 ± 1.20, 2(-ΔΔCt) 
): almost 2- to 4-fold enriched in comparison to samples from the healthy 
controls (less than 1.15 ± 0.34, 2(-ΔΔCt) ). To determine whether these miRNAs 
were related to the clinical features of children with DMD, we analyzed the 
associations compared to creatine kinase. There were very good inverse 
correlations between the levels of these miRNAs, especially miR-206, and 
functional performances: high levels corresponded to low muscle strength, muscle 
function, and quality of life. Moreover, by receiver operating characteristic 
curves analyses, we revealed that these miRNAs, especially miR-206, were able to 
discriminate DMD from controls. Thus, miR-206 and other muscle-specific miRNAs 
in serum are useful for monitoring the DMD pathological progression, and hence 
as potential non-invasive biomarkers for the disease. There has been a 
long-standing need for reliable, non-invasive biomarkers for Duchenne muscular 
dystrophy (DMD). We found that the levels of muscle-specific microRNAs, 
especially miR-206, in the serum of DMD were 2- to 4-fold higher than in the 
controls. High levels corresponded to low muscle strength, muscle function, and 
quality of life (QoL). These miRNAs were able to discriminate DMD from controls 
by receiver operating characteristic (ROC) curves analyses. Thus, miR-206 and 
other muscle-specific miRNAs are useful as non-invasive biomarkers for DMD.