Therefore, to evaluate age-specific differences between DMD group (DMD and clinically DMD) and BMD group (BMD and clinically BMD), we compared serum CK, CK/Cr, titin, and titin/Cr values in the 3–10, 11–15, 16–20, and 21–33-year age groups. Here, TTN is linked to Duchenne muscular dystrophy.