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Long-Read Sequencing 

Long-Read DMD Genetic Testing
For Dystrophinopathies 

About Dystrophinopathies 

Dystrophinopathies are a group of X-linked muscle disorders caused by mutations in the DMD gene, which encodes dystrophin—a protein essential for maintaining muscle cell integrity. The clinical spectrum includes:

  • Duchenne muscular dystrophy (DMD)

  • Becker muscular dystrophy (BMD)

  • DMD-associated X-linked dilated cardiomyopathy (XLDCM)

These disorders primarily affect skeletal muscle, cardiac muscle, or both. They predominantly affect males, although some females carrying a pathogenic DMD variant may also develop muscle weakness and/or cardiac involvement of varying severity. 

Genetic

The DMD gene spans approximately 2.2 Mb and contains 79 exons, with most of its sequence located in intronic regions. DMD disease-causing variants range from exon-level deletions (60-70%) and duplications (10%) to small sequence variants (18-20%), as well as other difficult-to-solve variants (2-5%) such as deep-intronic variants and complex structural rearrangements.¹⁻³

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Conventional testing, typically MLPA (deletion/duplication) analysis followed by NGS sequence analysis, identifies the cause in most patients. However, some cases remain unresolved because of limited intronic coverage or challenges in characterizing structural variants.²⁻³

Long-Read Sequencing on DMD Provides a More Complete Genetic View

Our LRS-DMD testing solution combines full-gene targeted capture with highly accurate HiFi long-read sequencing to analyze common and difficult-to-resolve variants in a single assay.

Full-Gene Coverage

Targeting the ~2.2 Mb full DMD gene, including exons and introns, our solution extends beyond exon-focused testing.

Streamlined Molecular Diagnosis

Integrated small-variant and structural-variant analysis simplifies laboratory workflows and can reduce the need for sequential testing, supporting a more efficient path to molecular diagnosis.

Precise Structural Variant Analysis

Go beyond copy-number detection with MLPA or microarray. LRS help pinpoint structural variant breakpoints, including those within exons, to support more accurate prediction of reading-frame disruption(in-frame or out-of-frame). LRS also clarify duplication arrangement, distinguishing tandem from dispersed duplications that may differ in clinical significance.

Resources

Send-out Testing

When considering our send-out sequencing services:

  1. Consultation: Contact our team for the most current test specifications.

  2. Sample Preparation: Check sample types and shipment requirements to ensure high-quality results. Please check your local export regulations and logistics partners.

  3. Submission: Contact Xcelom when placing an order. Include the completed Test Request and Consent Form, along with any required documents.

Sample Requirements

Peripheral Blood: 2 mL in EDTA tube

gDNA: > 3ug, band size >20 kb with no laddering or smearing

Transport Conditions

2-8℃, arrive within 72 hours

Reporting

Detects pathogenic, likely pathogenic, and selected variants of uncertain significance (VUS) associated with muscular dystrophy in the DMD gene, including SNVs, InDels, intragenic CNVs, and complex structural variants.

Turnaround Time (TAT)

25 working days

References:

1. Bladen CL, Salgado D, Monges S, et al. The TREAT-NMD DMD Global Database: analysis of more than 7,000 Duchenne muscular dystrophy mutations. Hum Mutat. 2015;36(4):395-402.

2. Zhao L, Pan S, Hu C, Shi Y, Li X. From shadows to clarity: A new paradigm for comprehensive variant detection in undiagnosed dystrophinopathy using combined long-read and RNA sequencing. Comput Struct Biotechnol J. 2025;27:5036-5044. 

3. Xie Z, Sun C, Liu Y, et al. Practical approach to the genetic diagnosis of unsolved dystrophinopathies: a stepwise strategy in the genomic era. J Med Genet. 2021;58(11):743-751. 

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