CKM and Duchenne muscular dystrophy: Fig 5 shows the plot of the ratio on the log2 scale against participants’ ages. We also compared this ratio to the values of serum CK muscle type (CKM) measured in a recent proteomics study [12]. All 51 of the DMD cases in the current study were also considered in the proteomics study. Overall, there was a negative correlation between CKM level and creatine/creatinine in the cases, reflecting a decrease in CKM activity that is most likely due to loss of muscle mass with age (S2 Fig).