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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Medical Genetics

Decoding Your Child's Genetic Report for DMD

At a Glance

A DMD genetic report is essential for confirming a Duchenne muscular dystrophy diagnosis and determining treatment eligibility. Knowing your child's exact mutation type and specific affected exons dictates whether they can receive targeted treatments like exon-skipping drugs or gene therapy.

In the past, a diagnosis of Duchenne Muscular Dystrophy (DMD) was confirmed by looking at a muscle sample under a microscope. Today, your child’s genetic report is the single most important document you will own [1]. It is no longer just a “confirmation” of the disease; it is a precision map that dictates which of the new, life-changing therapies your child can receive [2][3].

Types of Mutations: What is the “Typo”?

The DMD gene is one of the largest in the human body. Because it is so big, there are many ways a mutation (a “typo” in the code) can occur [4].

  • Large Deletions (approx. 65–70% of cases): One or more large sections (called exons) of the gene are missing [5][6].
  • Large Duplications (approx. 10–15% of cases): One or more exons are accidentally doubled or repeated [5][7].
  • Small Mutations / Point Mutations (approx. 15–20% of cases): A tiny change in a single “letter” of the genetic code. This includes nonsense mutations, which act like a premature “stop” sign in the middle of the gene [8][4].

Why the Exact Exons Matter

Modern treatments like exon-skipping drugs act like molecular “patches” designed for specific typos [9]. For example, if your child is missing Exons 48–50, they might be “amenable” to skipping Exon 51 to fix the link [10]. Without knowing exactly which exons are involved, a doctor cannot prescribe these precision medicines [11].

Similarly, the gene therapy Elevidys (delandistrogene moxeparvovec) is currently approved for patients with confirmed mutations, but doctors must check for specific deletions—specifically in Exons 8 and 9—as these can increase the risk of a serious immune reaction to the therapy [12][13].

Completeness Checklist: Is Your Report Ready?

A “complete” genetic report should answer these specific questions. If it doesn’t, your care team may need to order additional testing like Next-Generation Sequencing (NGS) [14].

  • [ ] Mutation Type: Does it clearly state if it’s a “Deletion,” “Duplication,” or “Point Mutation”? [6]
  • [ ] Exact Location: Does it list the specific exons affected (e.g., “Deletion of exons 45–50”)? [3]
  • [ ] Clinical Significance: Is the mutation labeled as “Pathogenic” (disease-causing)? [3]
  • [ ] Reading Frame: Does it specify if the mutation is “out-of-frame” (typical for DMD) or “in-frame” (typical for the milder Becker Muscular Dystrophy)? [15]

Is a Muscle Biopsy Still Necessary?

For the vast majority of children, a simple blood or saliva test is all that is needed for a definitive diagnosis [16].

However, a muscle biopsy (taking a small piece of muscle tissue) or a Western blot (measuring the amount of dystrophin protein) might still be required if:

  1. Genetic testing comes back normal but the child has clear symptoms and high CK levels [17].
  2. The genetic report finds a “Variant of Uncertain Significance” (a change that the lab hasn’t seen before and isn’t sure is harmful) [18].
  3. The mutation is “in-frame” (suggesting Becker), but the child’s symptoms are very severe (suggesting Duchenne) [15].

In these rare cases, looking directly at the protein in the muscle provides the final answer [17].

Return to the Home Page.

Common questions in this guide

Why is a genetic report important for Duchenne muscular dystrophy?
A genetic report identifies the exact mutation causing Duchenne muscular dystrophy. This information is no longer just for confirmation; it is a precision map that dictates which specific, life-changing therapies your child may be eligible to receive.
What is the most common type of DMD mutation?
Large deletions are the most common mutation, accounting for approximately 65 to 70 percent of cases. This means one or more large sections of the dystrophin gene, called exons, are missing.
Do specific mutations affect eligibility for DMD gene therapy?
Yes, certain gene therapies require doctors to check for specific genetic deletions. For example, deletions in Exons 8 and 9 can increase the risk of a serious immune reaction to certain gene therapies, which may affect your child's eligibility.
Is a muscle biopsy still necessary to diagnose DMD?
For most children, a genetic test using a blood or saliva sample provides a definitive diagnosis. A muscle biopsy is usually only needed if genetic testing is normal despite clear symptoms, or if the report shows a variant of uncertain significance.
What does an out-of-frame mutation mean on a DMD report?
An out-of-frame mutation completely disrupts the genetic code, which is typical for the more severe Duchenne muscular dystrophy. In contrast, an in-frame mutation usually leads to a milder form of the condition called Becker muscular dystrophy.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my child's report show a deletion, duplication, or point mutation?
  2. 2.Based on the exact exons listed here, is my child eligible for any of the four FDA-approved exon-skipping drugs?
  3. 3.Does my child have deletions in exons 8 or 9 that might make gene therapy riskier?
  4. 4.Is the mutation listed as 'pathogenic' or a 'variant of uncertain significance (VUS)'?
  5. 5.Is there any reason to perform a muscle biopsy, or is this genetic report definitive?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
  1. 1

    Duchenne muscular dystrophy.

    Duan D, Goemans N, Takeda S, et al.

    Nature reviews. Disease primers 2021; (7(1)):13 doi:10.1038/s41572-021-00248-3.

    PMID: 33602943
  2. 2

    Longitudinal effect of eteplirsen versus historical control on ambulation in Duchenne muscular dystrophy.

    Mendell JR, Goemans N, Lowes LP, et al.

    Annals of neurology 2016; (79(2)):257-71 doi:10.1002/ana.24555.

    PMID: 26573217
  3. 3

    Duchenne Muscular Dystrophy in Kazakhstan: A Journey from Diagnosis to the Treatment, the Biases and Achievements.

    Jaxybayeva A, Chunkayeva D, Myrzaliyeva B, et al.

    Journal of neuromuscular diseases 2023; (10(2)):263-269 doi:10.3233/JND-221559.

    PMID: 36641684
  4. 4

    Duchenne Muscular Dystrophy: From Diagnosis to Therapy.

    Falzarano MS, Scotton C, Passarelli C, Ferlini A

    Molecules (Basel, Switzerland) 2015; (20(10)):18168-84 doi:10.3390/molecules201018168.

    PMID: 26457695
  5. 5

    Molecular Diagnosis of Duchenne Muscular Dystrophy Using Single NGS-Based Assay.

    Nallamilli BRR, Guruju N, Jump V, et al.

    Current protocols 2023; (3(2)):e669 doi:10.1002/cpz1.669.

    PMID: 36748823
  6. 6

    EMQN best practice guidelines for genetic testing in dystrophinopathies.

    Fratter C, Dalgleish R, Allen SK, et al.

    European journal of human genetics : EJHG 2020; (28(9)):1141-1159 doi:10.1038/s41431-020-0643-7.

    PMID: 32424326
  7. 7

    The Genetic Landscape of Dystrophin Mutations in Italy: A Nationwide Study.

    Neri M, Rossi R, Trabanelli C, et al.

    Frontiers in genetics 2020; (11()):131 doi:10.3389/fgene.2020.00131.

    PMID: 32194622
  8. 8

    Spectrum of Genetic Variants in the Dystrophin Gene: A Single Centre Retrospective Analysis of 750 Duchenne and Becker Patients from Southern Italy.

    Viggiano E, Picillo E, Passamano L, et al.

    Genes 2023; (14(1)) doi:10.3390/genes14010214.

    PMID: 36672955
  9. 9

    Evolution and Breakthroughs in Exon Skipping and Splice Modulation: From Inception to Clinical Success.

    Lim KRQ, Yokota T

    Methods in molecular biology (Clifton, N.J.) 2025; (2964()):23-51 doi:10.1007/978-1-0716-4730-1_2.

    PMID: 40720009
  10. 10

    Pharmacological Profile of Viltolarsen for the Treatment of Duchenne Muscular Dystrophy: A Japanese Experience.

    Roshmi RR, Yokota T

    Clinical pharmacology : advances and applications 2021; (13()):235-242 doi:10.2147/CPAA.S288842.

    PMID: 34938127
  11. 11

    Targeting IRES-dependent translation as a novel approach for treating Duchenne muscular dystrophy.

    Péladeau C, Jasmin BJ

    RNA biology 2021; (18(9)):1238-1251 doi:10.1080/15476286.2020.1847894.

    PMID: 33164678
  12. 12

    Immunologic investigations into transgene directed immune-mediated myositis following delandistrogene moxeparvovec gene therapy.

    Potter RA, Moeller IH, Khan S, et al.

    Scientific reports 2025; (15(1)):4 doi:10.1038/s41598-024-84077-w.

    PMID: 39747998
  13. 13

    Practical Considerations for Delandistrogene Moxeparvovec Gene Therapy in Patients With Duchenne Muscular Dystrophy.

    Mendell JR, Proud C, Zaidman CM, et al.

    Pediatric neurology 2024; (153()):11-18 doi:10.1016/j.pediatrneurol.2024.01.003.

    PMID: 38306745
  14. 14

    A single NGS-based assay covering the entire genomic sequence of the DMD gene facilitates diagnostic and newborn screening confirmatory testing.

    Nallamilli BRR, Chaubey A, Valencia CA, et al.

    Human mutation 2021; (42(5)):626-638 doi:10.1002/humu.24191.

    PMID: 33644936
  15. 15

    Stepwise Diagnostic Strategy Integrating Long-Read Sequencing for the Interpretation of Phenotype-Genotype Discordance in Dystrophinopathy.

    Yuan Q, Liu C, Lu Y, et al.

    The application of clinical genetics 2025; (18()):243-249 doi:10.2147/TACG.S544691.

    PMID: 41341687
  16. 16

    Advances in Dystrophinopathy Diagnosis and Therapy.

    Saad FA, Siciliano G, Angelini C

    Biomolecules 2023; (13(9)) doi:10.3390/biom13091319.

    PMID: 37759719
  17. 17

    Unveiling non-coding DMD variants: synergising RNA sequencing and DNA sequencing for enhanced molecular diagnosis.

    Pan Y, Nallamilli BRR, Liu R, et al.

    Journal of medical genetics 2025; (62(2)):97-106 doi:10.1136/jmg-2024-110152.

    PMID: 39663110
  18. 18

    Delay in Diagnosis of Duchenne Muscular Dystrophy.

    Rao VK, Kuntz NL

    Pediatric neurology briefs 2015; (29(1)):5 doi:10.15844/pedneurbriefs-29-1-4.

    PMID: 26933528

This page explains DMD genetic testing for educational purposes. Your child's neurologist or genetic counselor is the best source for interpreting their specific lab report and treatment options.

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