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

Biallelic FGF14 expansions explain progressive gait imbalance

Clinical presentation

A 66-year-old male presented with the following symptoms:

  • Gait imbalance
  • Ataxia
  • Poor coordination
  • Dysarthria
  • Gaze-evoked nystagmus

Previous genetic testing

Multiple tests were performed with negative results including:

  • Ataxia panel
  • Whole exome sequencing

Genomic Unity® Testing

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

Genomic Unity® Testing

Variantyx Genomic Unity® testing identified pathogenic GAA expansions in both alleles of the FGF14 gene. Long-read sequencing confirmed both expansions, further characterizing the sizes as >300 repeats.

Diagnosis: Spinocerebellar ataxia 27B

View of FGF14 expansion variants

Uniform data from long-read WGS makes it possible to clearly size both expanded FGF14 alleles (partial sequences are shown).

The Variantyx Difference

Why was Genomic Unity® testing able to identify the previously missed biallelic FGF14 expansion?

  • Repeat expansions can not be detected by standard genetic tests, including panels and exomes.
    Variantyx genome analysis detects all major variant types in a single test including small sequence changes, structural variants, mitochondrial variants and repeat expansions. This is critical for ataxia patients where repeat expansions are a likely cause.

  • Ataxias are complex with variants in many different genes leading to similar symptoms.
    Only Variantyx testing covers 17 different ataxia repeat expansion genes.

  • FGF14 repeat expansions are rarely tested by other labs. When they are, other variant types are ignored.
    With Variantyx capabilities, analysis of FGF14 and other recessive short tandem repeat genes is available and always combined with analysis of additional variant types – all in one test.

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