This is a phase 4, multicenter, prospective, observational study designed to collect both medical history data and prospective data on Duchenne Muscular Dystrophy (DMD) treatment outcomes in participants receiving eteplirsen, golodirsen, and casimersen in routine clinical practice. Participants in this study will have been prescribed eteplirsen, golodirsen, or casimersen commercially prior to entry into the study.

Key Inclusion Criteria:

• Is willing to provide informed assent or consent (if applicable) and has a parent(s) or legal guardian(s) or is a participant ≥18 years of age who is (are) willing to provide informed consent for the participant to participate in the study and comply with study data collection procedures.
• Has an established clinical diagnosis of DMD, as documented prior to screening by a genetic report.
• Receiving, or initiating treatment with, eteplirsen, golodirsen, or casimersen at the time of observational study enrollment. Note: Participants with a prescription for eteplirsen, golodirsen, or casimersen at enrollment must initiate the exon-skipping therapy within 6 months of the date of enrollment or will no longer be eligible for this study. Note: Enrollment of eteplirsen participants has been completed, no additional participants will be enrolled.

Key Exclusion Criteria:

• Is currently participating in any DMD interventional study at the time of this study enrollment.

• Has declined to provide consent for collection of their genetic data.

• Has a medical condition or confounding circumstances that, in the opinion of the Investigator, might compromise:

  1. The participant's ability to comply with the protocol-required procedures
  2. The participant's wellbeing or safety, and/or
  3. The clinical interpretability of the data collected from the participant.

Other inclusion/exclusion criteria may apply.

Participants within each prescriber's practice who are receiving eteplirsen, golodirsen, or casimersen, in routine clinical practice, and who meet the study eligibility criteria and provide informed consent (either by the participant or through authorization by a legal guardian), will be invited to enroll into the study and will be followed according to the protocol.