Indeed, titin fragments were detected by mass spectrometric analysis in serums collected from young Duchenne muscular dystrophy (DMD) patients between the ages of 3 and 4 years old8, and comprehensive proteome studies of serum9 and urine10 of DMD patients and healthy donors revealed that titin showed the highest fold-change between healthy subjects and DMD patients. Here, TTN is linked to Duchenne muscular dystrophy.