MISSED BY OTHERS, DETECTED BY US
Genomic Unity® Case Study

CSTB repeat expansions explain refractory myoclonic epilepsy

Clinical presentation

A 20-year-old female presented with refractory myoclonic epilepsy accompanied by:

  • Myotonia
  • Ataxia and tremors
  • Dysarthria
  • Excessive daytime somnolence
  • Sleep terror
  • Anxiety and depression
  • Visual impairment
  • Bruising susceptibility

Previous genetic testing

Prior exome sequencing was negative, having identified a pathogenic variant in the recessive SCARB2 gene, but no second variant:

  • Whole exome sequencing

Genomic Unity® Testing

was ordered because of its ability to identify all major variant types in a single test.

Results and interpretation

Variantyx Genomic Unity® testing identified pathogenic CCCCGCCCCGCG expansions in both alleles of the CSTB gene. 

Long-read sequencing confirmed both expansions, further characterizing the sizes as 53-54 repeats each.

Diagnosis: Progressive myoclonic epilepsy

CSTB repeat expansions

Uniform data from long-read WGS makes it possible to clearly size the CSTB alleles (partial sequences are shown).

The Variantyx Difference

Why was Genomic Unity® testing able to identify the previously missed CSTB expansions?

  • Repeat expansions can not be detected by standard genetic tests, including exomes.
    Variantyx genome analysis detects all major variant types in a single test including small sequence changes, mitochondrial variants, structural variants, and repeat expansions.
    It easily detected the expanded CSTB alleles while simultaneously ruling out a second SCARB2 variant.

Want similar results for your patients?

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