If the DMD gene is out of tune, it can affect the whole performance.1

But with gene therapy, it may one day achieve better harmony.1


Reimagine Duchenne is an invitation to learn more
about the potential of gene therapy. Gene therapy is
being studied to add some of the functional protein
children with Duchenne muscular dystrophy need.1


Pfizer's gene therapy for Duchenne muscular dystrophy is being evaluated in clinical trials and is not approved by the FDA. If FDA approved, it may not be an appropriate treatment for all children with Duchenne.

An overview of Duchenne

To understand Duchenne muscular dystrophy (Duchenne or DMD) and the potential of gene therapy, it helps to understand what genes are.

Genes are DNA segments that instruct specific protein production to help build and maintain our bodies. Every cell of the body counts on proteins to provide structure, support, and even instructions to carry out their work.2

The role of the DMD gene specifically is to produce a protein called dystrophin (pronounced di·struh·fin) . Duchenne happens due to mutations in the DMD gene, preventing the production of dystrophin.1,3 This gene mutation may be passed down from a parent to child but may also occur randomly.4 A mutation is when a part or parts of a gene differ from what’s expected.5 Many mutations in genes have no effect on the functioning of the gene, and most do not cause disease.5

Understanding the types of DMD gene mutations

The DMD gene is the body's longest gene.6 A mutation to any part of this gene can lead to Duchenne.1,4 A deletion mutation is most common in Duchenne.1 There are two types of deletion mutations, in-frame and out-of-frame. If a deletion is in-frame, the DMD gene is maintained and not disrupted, which means it is present but is shorter than normal.1,4 An out-of-frame deletion is when part of the DMD gene is missing. An out-of-frame deletion can lead to Duchenne.1,4 Duplication mutations, where part of the gene is repeated, can also cause Duchenne.3 Deletion mutations and duplication mutations account for 70-80% of Duchenne cases.3 Other cases are caused by a point mutation, which impacts a very small portion of a part of the DMD gene.3

See below for visual examples of the different types of mutations in the DMD gene:

No mutation

DMD gene

DNA strand with no mutation

Deletion mutation

Part of the gene is missing3

DNA strand with part missing

Duplication mutation

Part of the gene is repeated3

DNA strand with part repeated

Point mutation

Small portion of a part of the gene is added, deleted, or changed3

DNA strand with part added, deleted, or changed

From gene to protein - the role of dystrophin

All proteins have special roles in the body.7 A protein that’s important to the body's muscles and organs, such as the brain and heart, is dystrophin.1 It protects muscles during movement, and acts almost like a shock absorber.4 Children living with Duchenne can't make the dystrophin their muscles need.1

Who does Duchenne affect?

There are about


boys living with

Duchenne in the US.8

For every

male babies

born in the US, it’s estimated that about

19 of them will have Duchenne.8

The different stages of Duchenne
and how it’s diagnosed


Recognizing the signs, symptoms, and progression of Duchenne

The progression of Duchenne may vary from child to child. Early on, the impact of muscle weakness may be limited to movement and walking. Over time, muscle damage builds, and continued loss of muscle then impacts more of the body, including the heart and the muscles that affect how the lungs function.9,10

One early sign that is common to Duchenne is Gowers' sign.1 This is when the child rises from the floor by starting on their hands and knees and then "walking" their hands up their legs. Read on for some other potential signs of Duchenne over time.1

Silhouette of early-stage child

Early stage

0+ years old*10

Pre-symptomatic/ diagnosis10

Silhouette of middle-stage child

Middle stage

8+ years old*10,11

(able to walk independently)10,11

  • Leg muscle aches10
  • Having trouble walking12
  • Losing ability to climb stairs and stand up from the floor10
  • Achilles tendon tightening known as a contracture11
Silhouette of late-stage child in wheelchair

Late stage

12+ years old*10,11

(no longer walking independently)10,11

  • Increasing loss of upper limb function10
  • Not able to maintain posture10
  • Develop scoliosis, a curve in the spine11
  • Function in the lungs is declining and may need breathing assistance11
  • Function in the heart is declining11

*Ages and stages may vary depending on each child.

Duchenne testing – at diagnosis and over time

Diagnosis is based on key signs, medical history, and several tests.

Blood tests

  • Creatine kinase-MM test – A test that looks for high levels of CK-MM in the blood, which can signal muscle damage. By itself, a high CK-MM level is not enough to know for sure if a child has Duchenne, as there can be other causes for this.1,9
  • Genetic test – A test used to confirm the presence and type of DMD gene mutation. Genetic testing can be done at any point in the diagnosis journey.9,10

Muscle biopsy

If signs, history, and blood tests (including genetic testing) are not enough to make a diagnosis, a muscle biopsy may be needed. For this procedure, the doctor will remove a very small amount of the muscle to test if it has dystrophin. The doctor will then use the results to confirm the diagnosis.9

Young child surrounded by their parents and care team

Finding a team of specialists is a key step when caring for a child with Duchenne.10

A neuromuscular specialist helps understand nerve and muscle diseases. This specialist usually makes the diagnosis of Duchenne and leads the care team. The care team provides all-around care for children living with Duchenne and may recommend other specialists.9

Duchenne can also affect the heart and how the lungs function. That’s why both a pulmonologist and a cardiologist may be part of the care team. Other care team members may include a primary care doctor, a physical therapist, an occupational therapist, and others.10

The care team will track Duchenne over time with a series of functional tests

The care team for a child living with Duchenne will track how their symptoms change over time. To do this, a neuromuscular specialist or a physical therapist may use special tests to assess the impact of Duchenne and the child's ability to move.10,13 These tests may include the North Star Ambulatory Assessment (NSAA), the 6-minute walk test (6MWT), the 10-meter walk test (10MWT), and the timed rise from floor test (TRF).13,14,15 These tests are commonly used by physicians to measure functional motor abilities.9

It is important for the care team to keep track of a child's progress so they can monitor any changes to see if they need additional support.

For illustration purposes only.
Young child jumping
Example NSAA Test: Jump

NSAA tracks changes in 17 key movements12

The NSAA includes 17 tests to measure functional skills.12 These include sitting, standing, walking, jumping, and getting up from a chair. A member of the care team will grade each test with a score from 0-2. These scores are based on whether the child can perform the movement and how well they can do it.12 A child with Duchenne may show improvements in their score due to either the natural course of disease or due to treatment.16,17

For illustration purposes only.
Young child walking
Example Test: 6-minute walk test

Walking tests help track endurance and assess loss of gait18,19

A care team member will use the 6-minute walk test (6MWT) to assess the distance a child with Duchenne can walk within 6 minutes.13 After the test is performed, the doctor can track the progression of muscle function as well as the child's endurance.18

The 10-meter walk test (10MWT) may be used to evaluate the time it takes for a child with Duchenne to walk 10 meters.15 This test can help the doctor measure the child's manner of walking, known as their "gait," over time.19

For illustration purposes only.
Young child rising up from the floor
Example Test: Timed rise from floor test

The timed rise from floor test (TRF) helps track the progression of Duchenne14

The timed rise from floor test measures the time it takes a child lying face-up to stand.14 It is often performed at the same time as the NSAA test.14 The child will only be timed if they are able to complete this test. The TRF test helps the care team track the child's movement and disease progression over time.14

Science and medicine are evolving the care of Duchenne

Depending on your child's needs or progression of disease, you and your child's care team will determine how to best manage their care. Studies for more treatment options for Duchenne are ongoing.10

The care team approach has improved the length and quality of life for children living with Duchenne.9

Learn how an out-of-tune DMD gene can affect the whole performance

Learn how an out-of-tune DMD gene can affect the whole performance
Learn how an out-of-tune DMD gene can affect the whole performance

See the potential of gene therapy for Duchenne and learn about how it may work.

Discover the science of gene therapy

1. Duan D, Goemans N, Takeda S, Mercuri E, Aartsma-Rus A. Duchenne muscular dystrophy. Nat Rev Dis Primers. 2021:7(1):13. doi:https://doi.org/10.1038/s41572-021-00248-3. Accessed August 1, 2023. 2. MedlinePlus. Help me understand genetics: MedlinePlus genetics. Medlineplus.gov. medlineplus.gov/genetics/understanding/. Accessed August 1, 2023. 3. Types of Mutations - Parent Project Muscular Dystrophy. Parent Project Muscular Dystrophy, 2017. www.parentprojectmd.org/about-duchenne/what-is-duchenne/types-of-mutations/. Accessed August 1, 2023. 4. Aartsma-Rus A, Ginjaar IB, Bushby K. The importance of genetic diagnosis for Duchenne muscular dystrophy. Journal of Medical Genetics. 2016;53(3):145-151. doi:https://doi.org/10.1136/jmedgenet-2015-103387. Accessed August 1, 2023. 5. Gilchrist DA. Mutation. Genome.gov. National Human Genome Research Institute, 2019. www.genome.gov/genetics-glossary/Mutation. Accessed August 1, 2023. 6. Gao, Quan Q, Elizabeth M McNally. The Dystrophin Complex: Structure, Function, and Implications for Therapy. Comprehensive Physiology, U.S. National Library of Medicine, 1 July 2015. www.ncbi.nlm.nih.gov/pmc/articles/PMC4767260/. Accessed August 1, 2023. 7. MedlinePlus. What are proteins and what do they do? Medlineplus.gov. Published March 26, 2021. https://medlineplus.gov/genetics/understanding/howgeneswork/protein/. Accessed August 1, 2023. 8. Giegerich E, Stuntz M. PMS30 Duchenne muscular dystrophy prevalence in the US: a novel incidence-based modeling approach using system dynamics. Value in Health. 2019;22(2): S244. doi:https://doi.org/10.1016/j.jval.2019.04.1140. Accessed November 13, 2023. 9. Birnkrant DJ, Bushby K, Bann CM, et al. Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and neuromuscular, rehabilitation, endocrine, and gastrointestinal and nutritional management. Lancet Neurol. 2018;17(3):251-267. doi:https://doi.org/10.1016/s1474-4422(18)30024-3. Accessed August 1, 2023. 10. Bushby K, Finkel R, Birnkrant DJ, et al. Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and pharmacological and psychosocial management. Lancet Neurol. 2010;9(1):77-93. doi:https://doi.org/10.1016/s1474-4422(09)70271-6. Accessed August 1, 2023. 11. Duchenne Muscular Dystrophy: Causes, Symptoms, and Treatment | Pfizer. https://www.pfizer.com/disease-and-conditions/duchenne-muscular-dystrophy#:~:text=About%20250%2C000%20people%20in%20the. Accessed August 1, 2023. 12. North Star Ambulatory Assessment (NSAA). V2.1 September 30, 2020. https://www.musculardystrophyuk.org/static/s3fs-public/2021-08/NSAA%20_Manual_%2015102020.pdf?VersionId=BaPGDWk5TxA3rtF2DDipAVYlOJ5Eoumo. Accessed November 16, 2023. 13. Matos Casano HA, Anjum F. Six-Minute Walk Test. Statpearls. NCBI Bookshelf. www.ncbi.nlm.nih.gov/books/NBK576420/. Accessed August 1, 2023. 14. Mazzone ES, Coratti G, Sormani MP, et al. Timed Rise from Floor as a Predictor of Disease Progression in Duchenne Muscular Dystrophy: An Observational Study. PLoS One. 2016;11(3):e0151445. Published 2016 Mar 16. doi:10.1371/journal.pone.0151445. Accessed November 16, 2023. 15. de Baptista C, Vicente AM, Souza MA, Cardoso J, Ramalho VM, Mattiello-Sverzut AC. Methods of 10-Meter Walk Test and Repercussions for Reliability Obtained in Typically Developing Children. Rehabil Res Pract. U.S. National Library of Medicine, 20 Aug. 2020, www.ncbi.nlm.nih.gov/pmc/articles/PMC7455832/. Accessed November 16, 2023. 16. De Sanctis R, Pane M, Sivo S, et al. Suitability of North Star Ambulatory Assessment in young boys with Duchenne muscular dystrophy. Neuromuscul Disord. 2015;25(1):14-18. doi:10.1016/j.nmd.2014.09.015. Accessed August 1, 2023. 17. Muntoni F, Domingos J, Manzur A, et al. Categorising trajectories and individual item changes of the North Star Ambulatory Assessment in patients with Duchenne muscular dystrophy. PLoS ONE. 2019;14(9). doi:https://doi.org/10.1371/journal.pone.0221097. Accessed August 1, 2023. 18. McDonald CM, Henricson EK, Abresch RT, et al. The 6-minute walk test and other clinical endpoints in Duchenne muscular dystrophy: reliability, concurrent validity, and minimal clinically important differences from a multicenter study. US National Library of Medicine. Muscle Nerve. 2013; 48:357-368. doi:https://doi.org/10.1002/mus.23905. Accessed November 28, 2023. 19. Pizzato TM, de Baptista CA, Martinez EZ, da Rosa Sobreira CF, Mattiello-Sverzut. Prediction of loss of gait in Duchenne muscular dystrophy using the ten meter walking test rates. J Genet Syndr Gene Ther. 2016; 7(4). doi:https://doi.org/10.4172/2157-7412.1000306. Accessed November 28, 2023.