Duchenne Muscular Dystrophy (DMD)


Muscular dystrophy (MD) is a group of genetic diseases characterized by progressive muscle weakness and atrophy. There is currently no cure for any form of MD but there are treatment options that can alleviate symptoms and increase patients’ quality of life. These include physical therapy, occupational therapy, speech therapy, respiratory therapy, surgery, and drug therapies.

Physical Therapy

Physical therapy can help strengthen muscles that are affected by MD and prevent contracture. An exercise routine tailored for the patient’s needs can be performed initially under the supervision of a physiotherapist and then at home.1 These exercises can improve not only muscle strength and range of motion, but they can also increase patients’ self-esteem and well-being. 

MD in the UK developed an online eLearning module on neuromuscular conditions for physiotherapists. The module consists of 11 short topics to help physiotherapists manage muscular dystrophy.2

Occupational Therapy

Occupational therapy can help patients with MD continue to perform daily activities as independently as possible. It can also teach patients how to use aids and adaptations such as wheelchairs, which will make their daily living easier.1

Occupational therapists can work together with health care teams to ensure programs specific to each patient’s needs are implemented. They can also work with the patients’ school or workplace to help patients reach their full potential and maintain their independence.

The  UK has an MD occupational therapist’s network, which offers the latest information about MD tailored to occupational therapists’ professional needs.3

Speech Therapy

Certain types of MD can affect the muscles used for swallowing and speech. This can cause dysphagia and dysarthria. Speech therapy can help improve speech through language intervention activities, articulation therapy, and oral motor therapy.4 

In advanced stages of MD, patients may need augmentative and alternative communication support, which speech therapists can help with.

Respiratory Therapy

Most types of MD affect respiratory muscles as they progress. This causes respiratory insufficiency and leads to frequent lung infections.

Respiratory therapists can perform lung function tests and sleep studies to assess patients’ respiratory function. They can manage lung volume recruitment, provide manual and mechanically assisted coughing, and advise on noninvasive ventilation with associated interfaces, tracheostomies, and mechanical ventilators.5

Surgery

MD can cause complications such as cardiomyopathy and scoliosis. Depending on the type of MD patients have, different types of surgery are warranted. For example, some patients may need spinal surgery to treat their scoliosis, while others need tendon release surgery to treat contracture. Other orthopedic surgeries that muscular dystrophy patients may need include hip, knee, and ankle surgery (lengthening or tenotomy of the Achilles tendon).6

Some patients may need cataract surgery and some may need a pacemaker or cardiac defibrillators to manage their abnormal heart rhythm conditions.7

Drug Therapy

Corticosteroids may be prescribed for some types of MD to delay the progression of the disease and allow patients to maintain ambulation for as long as possible.8 

Corticosteroids work by reducing inflammation and strengthening muscle cell membranes, thereby preserving muscle strength. However, they can have severe side effects especially with prolonged use including weight gain, osteoporosis, glaucoma, and hypertension.9

The main corticosteroids prescribed to treat people with muscular dystrophy are deflazacort and prednisone.

Gene-Based Therapies

There are also a number of gene-based therapies that have been recently approved by the US Food and Drug Administration (FDA) to treat certain types of muscular dystrophy such as Duchenne muscular dystrophy (DMD). These are the exon-skipping therapies Exondys 51 (eteplirsen), Vyondys 53 (golodirsen), and Amondys 45 (casimersen).10,11,12

Exon skipping uses antisense oligonucleotides to mask certain exons to restore the reading frame of a gene.13 DMD can be caused by the deletion of large areas in the DMD gene or point mutations, which both disrupt the reading frame of the gene leading to no dystrophin protein being produced. Exon skipping can ensure that a shorter still functional dystrophin protein is made by cells. Different exons need to be skipped to restore the reading frame of the gene depending on the causative mutation, so not every exon-skipping drug is efficient in all DMD patients.

There are also other gene-based therapies that are currently in clinical trials for the treatment of muscular dystrophy. These include the stop codon read-through therapy Translarna™ (ataluren), which reverses the effect of nonsense mutations and which is already authorized for use in the EU to treat some patients with DMD,14 and therapies that aim to deliver a healthy copy of the disease-causing gene to the body using an adeno-associated virus (AAV).15

References

  1. Therapy for muscular dystrophy. NYU Langone Health. Accessed May 24, 2021.
  2. Adult physiotherapy e-learning module. Muscular Dystrophy UK. Accessed May 24, 2021.
  3. For occupational therapists. Muscular Dystrophy UK. Accessed May 24, 2021.
  4. Speech-language therapy. Kids Health. September 2019. Accessed June 25, 2021.
  5. Sheehan DW, Birnkrant  DJ, Benditt JO, et al. Respiratory management of the patient with Duchenne muscular dystrophy. Pediatrics. 2018;142(Suppl 2):S62-S71. doi:10.1542/peds.2018-0333H 
  6. Griffet J, Decrocq L, Rauscent H, Richelme C, Fournier M. Lower extremity surgery in muscular dystrophy. Orthop Traumatol Surg Res. 2011;97(6):634-8. doi:10.1016/j.otsr.2011.04.010
  7. Surgery for muscular dystrophy. NYU Langone Health. Accessed May 24, 2021.
  8. Angelini C. The role of corticosteroids in muscular dystrophy: a critical appraisal. Muscle Nerve. 2007;36(4):424-35. doi:10.1002/mus.20812
  9. Prednisone and other corticosteroids. Mayo Clinic. Accessed May 24, 2021. 
  10. Lim KR, Maruyama R, Yokota T. Eteplirsen in the treatment of Duchenne muscular dystrophy. Drug Des Devel Ther. 2017;11:533-545. doi:10.2147/DDDT.S97635
  11. Golodirsen (Vyondys 53) for Duchenne muscular dystrophy. Med Lett Drugs Ther. 2020;27;62(1603):119-120. PMID: 32728014.
  12. Shirley M. Casimersen: first approval. Drugs. 2021;81(7):875-879. doi:10.1007/s40265-021-01512-2 
  13. What is exon skipping and how does it work? Muscular Dystrophy UK. Accessed May 24, 2021.
  14. Translarna. European Medicines Agency.
  15. Crudele JM, Chamberlain JS. AAV-based gene therapies for the muscular dystrophies. Hum Mol Genet. 2019;1;28(R1):R102-R107. doi:10.1093/hmg/ddz128

Article reviewed by Debjyoti Talukdar, MD, on July 1, 2021.