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Long-Read Sequencing 

Comprehensive Analysis of Mucopolysaccharidosis II (CAMPS II)

The Premier Solution for Hunter Syndrome and IDS Analysis

MPSII/ Hunter Syndrome: Genetics and Testing Challenges

Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome, is X-linked recessive lysosomal storage disorder, caused by IDS gene defect. The condition presents a wide phenotypic spectrum, classified into attenuated and severe forms. Standard stepwise biochemical and enzyme activity testing often results in delayed diagnosis. Crucially, these methods are frequently unsuitable for female heterozygous or prenatal samples, creating a critical gap in family planning and early intervention.

 

Although genetic testing using NGS, PCR, and Sanger sequencing can support a differential diagnosis, they face significant limitations. The IDS gene has a highly homologous pseudogene, IDSP1. This results in limited mappability on short-read NGS platforms due to sequence similarity. Approximately 15% of cases involve complex structural variations, such as large insertions/deletions and rearrangements between IDS and IDSP1.¹ Given this complex molecular nature, routine genetic assays carry a significant risk of missing causative variants.

Advancing Molecular Diagnostics with Long-Read Sequencing (LRS)

Comprehensive Analysis of Mucopolysaccharidosis II (CAMPS II) utilizes PacBio SMRT technology to sequence the full-length of the IDS gene and part of pseudogene IDSP1 in a single assay.

  • Accurately distinguishes between the IDS and the pseudogene IDSP1

  • Successfully identifies structural variants with precise breakpoints, including large insertions/deletions and inversions

  • Replaces the need for multiple, stepwise tests

Proven Diagnostic Outcome

  • 100% Detection Rate: IDS variants were identified in all patients

  • 16.3% Higher Diagnostic Yield: CAMPS II identified pathogenic/likely pathogenic variants in 82.6% of patients, compared to only 66.3% by conventional methods

  • 14.1% of patients were found to carry novel variants

A total of 173 participants (92 unrelated patients and 81 relatives) were comparatively tested with Sanger sequencing + MLPA vs. CAMPSII ²

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

Dried Blood Spot (DBS): 3 spots, ≥ 8mm diameter each

gDNA: >10 ng/uL and >30 nL

Transport Conditions

2-8℃, arrive within 72 hours

Testing Scope

Detects the IDS variants, including:

  • SNVs/InDels classified as P/LP and selected VUS

  • Selected intragenic deletions/duplications classified as P, LP or VUS

  • Intron 7 inversion

  • Exon 2-intron 3 inversion

Turnaround Time (TAT)

17 working days

Resources

References:

1. Zanetti A, D'Avanzo F, Tomanin R. Molecular basis of mucopolysaccharidosis type II (Hunter syndrome): first review and classification of published IDS gene variants. Hum Genomics. 2024;18(1):134.

2. Hao N, Yao F, Li D, et al. Long-Read Sequencing Expands the Genotypic Spectrum of Patients With Mucopolysaccharidosis Type II. J Inherit Metab Dis. 2025;48(4):e70055.

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