Natural History of Duchenne Muscular Dystrophy

Inclusion Criteria:

1. Male
2. 5 to 9 years old inclusive
3. Body-Weight < or = 75th percentile of BMI body-mass index scale (according tovalidated scale in force in the country site)
4. Diagnosis of DMD based upon Gene testing positive with detailed genotyping
5. Able to achieve:

• NSAA (North Star Ambulatory Assessment) scale > or =18 (with a maximum of 2points difference between inclusion and screening visits) and/or:
• Gowers test < or =7 sec
• 6 Minute Walk Test (6MWT) > or = 350 meters at screening visit (M1) and atinclusion visit (M0) with the distance being 20% of each other

6. Ongoing corticosteroid therapy or initiation of corticosteroid therapy according tostandard of care in the previous 3 months
7. Signed informed consent by at least one parent(s) or both parents or legal guardianrepresentative(s), when applicable and according to the country regulation
8. Affiliated Beneficiary of the National Health Care scheme

Exclusion Criteria: 9. Cardiomyopathy based on physical cardiological examination and echocardiography withLeft Ventricular Ejection Fraction (LVEF) below 55% 10. Respiratory Assistance: need for either a diurnal and/or a nocturnal ventilation 11. Any co-morbidity (ies) and or previous or planned surgical event(s) which mayinterfere with DMD natural evolution and or evaluation of outcomes designed to assessDMD Natural History 12. Muscle testing: inability to cooperate with 13. Nuclear Magnetic Resonance Imaging (NMRI): metal implants in regions of interest forthe study 14. Unwilling and/or unable to comply with all the study protocol requirements and orprocedures 15. Previous inclusion to another clinical trial with an Investigational Medicinal Product (IMP), within the 3 months (or IMP washout period) prior to the screening visit of thestudy 16. Concomitant participation to any other clinical trial