Introduction: Duchenne muscular dystrophy (DMD) is a genetic disease related to mutations in the dystrophin gene, with symptoms of progressive muscle weakness beginning in early childhood. There is a need for biomarkers to monitor disease progression, and muscle ultrasound is being studied as an auxiliary examination to detect different degrees of muscle involvement. Objectives: o evaluate the potential of quantitative muscle ultrasound (QMUS) as biomarkers of progressive muscle impairment, and their correlation with pulmonary and motor function in Duchenne muscular dystrophy patients at different disease stages. Methods: This was a prospective observational study that included 53 male patients, aged between 5 and 18 years, with a genetic diagnosis of DMD. Patients underwent a protocol of muscle ultrasound, pulmonary function, and motor function assessments over 24 months. The muscle ultrasound protocol was performed on 12 muscles, followed by quantitative analysis of echogenicity (Gray-Scale Analysis – GSA) and histogram generation. Patients also underwent pulmonary function assessment and motor function assessment using the MFM-32 (Motor Function Measure) scale. The ultrasound protocol was also performed on a control group (single assessment). Results: Fifty-three patients with a mean age of 11.5 years were included. Our study robustly distinguished participants with DMD from healthy individuals in all studied muscles using quantitative ultrasound by GSA (p<0.001), with a consistent pattern of increased muscle echogenicity in older patients and with predominance in proximal muscles. The results demonstrated a significant correlation between quantitative ultrasound with the functional measures of the MFM-32 scale, indicating that greater echogenicity (greater muscle degeneration) is associated with worse motor performance. Change sensitivity analysis (SRM) to evaluate QMUS's sensitivity in detecting changes over time showed more substantial changes in echogenicity (SRM>0.8) for the deltoid, first interosseous, intercostal, rectus abdominis, tibialis anterior, and medial gastrocnemius muscles. Conclusion: QMUS can be used as a biomarker of progression in Duchenne muscular dystrophy in patients aged 6 to 18 years, demonstrating increased echogenicity both in comparison to healthy patients and in older boys, in addition to a correlation with the MFM-32 motor scale and high sensitivity to changes over time (SRM>0.8) for the deltoid, first interosseous, rectu