Muscular dystrophies

Last reviewed: 26 Aug 2023
Last updated: 01 Aug 2023
01 Aug 2023

FDA approves first gene therapy for treating Duchenne muscular dystrophy

​Delandistrogene moxeparvovec was approved by the Food and Drug Administration (FDA) in June 2023 for the treatment of ambulatory patients ages 4-5 years with Duchenne muscular dystrophy (DMD) who have a confirmed mutation in the DMD gene and do not have a pre-existing medical reason preventing treatment with the therapy. Approval was granted via the accelerated approval pathway.

Delandistrogene moxeparvovec is a recombinant adeno-associated virus vector-based gene therapy designed to deliver a gene that leads to expression of a microdystrophin comprising key functional domains of the normal dystrophin protein. It is administered as a single intravenous dose.

The approval was based on analysis of results submitted to the FDA from randomized trials indicating that the microdystrophin was expressed in patients treated with the therapy. A clinically meaningful and statistically significant difference in North Star Ambulatory Assessment score was reported for patients treated with delandistrogene moxeparvovec compared with a propensity-score-weighted external control cohort after 1 year.[74]​ Adverse effects noted in the trials included myocarditis, elevations of troponin-I, acute liver injury, and thrombocytopenia. Studies are ongoing to demonstrate clinical benefit.

See Management: emerging

Original source of update



History and exam

Key diagnostic factors

  • family history of DMD
  • male sex
  • imbalance of lower limb strength
  • lower extremity musculotendinous contractures
  • delayed motor milestones
  • calf hypertrophy
  • ambulation difficulty and falls
  • diminished muscle tone and deep tendon reflexes
  • normal sensation
  • Gowers sign
More key diagnostic factors

Other diagnostic factors

  • toe walking
  • hypotonia
  • hyperactivity
  • urinary and bowel incontinence
  • mild to severe intellectual disability
Other diagnostic factors

Risk factors

  • family history
  • male sex
More risk factors

Diagnostic investigations

1st investigations to order

  • serum creatine kinase (CK)
  • genetic testing
More 1st investigations to order

Investigations to consider

  • electromyogram (EMG)
  • muscle biopsy
  • muscle MRI
More investigations to consider

Treatment algorithm


DMD: ambulatory stage

DMD: early nonambulatory stage

DMD: late nonambulatory stage

spinal muscular atrophy (SMA)



Pinki Munot, MD

Consultant Paediatric Neurologist

Great Ormond Street Hospital for Children




PM is a principal investigator for the Sideros trial in DMD and the ARGNX trial in Myasthenia, and a sub-investigator for the SHINE trial. PM was reimbursed for presenting at the PULSE 65 rare disease day for GPs in December 2023 and for the RCPCH 2022 lunch time symposium by PTC therapeutics.


Dr Pinki Munot would like to gratefully acknowledge Dr John R. Bach, Dr Aravindhan Veerapandiyan, and Dr Bilal Saulat, previous contributors to this topic.


JRB, AV, and BS declare that they have no competing interests.

Peer reviewers

Lisa D. Hobson-Webb, MD

Assistant Professor of Medicine

Department of Medicine/Neurology

Duke University Medical Center




LDH-W declares that she has no competing interests.

Martin K. Childers, DO, PhD

Associate Professor Neurology and Regenerative Medicine

Wake Forest University Health Sciences




MKC declares that he has no competing interests.

Adnan Manzur, FRCPCH

Consultant Paediatric Neurologist

Great Ormond Street Hospital for Children NHS Trust




AM has been paid an honorarium for giving lectures at the Imperial College Educative Training Courses for GPs and post-graduate doctors. AM is the lead author of the Cochrane review of corticosteroids in Duchenne muscular dystrophy. He is also the Lead Clinician of the NorthStar Clinical Network for Management of Neuromuscular Disorders in the UK.

Richard W. Orrell, BSc, MD, FRCP

Senior Lecturer and Consultant Neurologist

Department of Clinical Neuroscience

UCL Institute of Neurology




RWO is an author of a reference cited in this topic.

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