To characterize the natural history and progression of Duchenne Muscular Dystrophy (DMD) to help inform the design of future studies, to capture biomarkers of safety and disease progression and to provide comparative data for the development of rare exons for which formal controlled trials are not feasible.

This is a prospective study. All DMD patients that fulfil the inclusion/exclusion criteria are eligible although the study is weighted towards ambulant subjects aged 3 years or older. There will be 7 study visits and subjects will be in the study for a maximum of 3 years. Visits will occur every 6 months (+/- 1 month).

Up to 250 DMD subjects planned in the following categories :

• 75 % ambulant subjects aged between 3 and 18 years at study entry
• 25% non-ambulant subjects with a maximum age of 18 years at study entry

Subjects will be asked to perform muscle testing assessment with a clinical evaluator, such as walking for 6 minutes, climb stairs, breathe in a tube, see how they can move their arms and legs. They will be asked questions about how they feel overall and perform daily activities. These measurements will be assessed every 6 months.

Urine and blood samples will be collected once a year to measure biomarkers that will allow to have a better overview of DMD.

Inclusion Criteria:

• Diagnosis of DMD resulting from a mutation in the DMD gene confirmed by a state of the art DNA diagnostic technique covering all DMD gene exons.
• Age 3 - 18 years
• Willing and able to comply with protocol requirements
• Life expectancy of at least 3 years
• Able to give informed assent and/or consent in writing signed by the subject and/or parent(s)/legal guardian (according to local regulations)

Exclusion Criteria:

• Current participation in a clinical study with an Investigational Medicinal Product (IMP)
• Participation within the previous 1 month in a clinical study with an IMP

Subjects diagnosed with DMD resulting from a mutation in the DMD gene which is confirmed by a state of the art DNA diagnostic technique covering all DMD gene exons