MISSED BY OTHERS, DETECTED BY US
IriSight® Case Study

Compound heterozygous sequence variants explain hydrops fetalis in second pregnancy loss

Clinical presentation

A couple presented with their second pregnancy with nonimmune hydrops, without other anomalies, in midgestation. Hydrops was identified in the first pregnancy therefore nuchal translucency in this pregnancy was tested and found to be normal (1.7mm).

  • Nonimmune hydrops

Previous genetic testing

Multiple tests were performed for the first pregnancy including karyotype, chromosomal microarray and PWS/AS methylation – all with negative results. Tests performed during the second pregnancy, and later on the products of conception (POC), were also negative including:

  • cfDNA screening
  • Chromosomal microarray

IriSight® Testing

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

Results and interpretation

Variantyx IriSight® testing identified maternally and paternally inherited, compound heterozygous, pathogenic variants in the PIEZO1 gene.

Both variants result in early termination of the protein.

Diagnosis: Lymphatic malformation type 6

IGV view of PIEZO1 variants

Uniform data from WGS clearly shows both variants and the pattern of inheritance.

The Variantyx Difference

Why were these compound heterozygous sequence variants detected by IriSight® testing, and not detected by other tests?

  • Single nucleotide variants (SNVs) are not detectable by karyotype, chromosomal microarray or cfDNA technologies which represent the majority of products of conception (POC) offerings.
    With a detection range from 1 bp to whole chromosomal events, Variantyx genome analysis is able to detect aneuploidy, CNVs and single nucleotide changes within a single test.

  • POC samples are rarely accepted for targeted panel testing and exome testing is typically not made available until after aneuploidy has been ruled out, extending the diagnostic odyssey.
    Variantyx genome analysis provides comprehensive coverage of all major clinically-relevant variant types and all genes within a single test, eliminating the need for sequential, often inaccessible, follow-on testing.

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