MISSED BY OTHERS, DETECTED BY US
IriSight® Case Study

Single exon DOK7 deletion explains arthrogryposis multiplex congenita

Clinical presentation

A multigravida underwent an anatomy scan at 22 weeks gestation. In addition to IUGR and minimal fetal movement, the following fetal findings were noted:

  • Non-immune hydrops, fetal ascites, pleural effusion
  • Hand clenching, club foot, rocker bottom feet
  • Short long bone
  • Arthrogryposis multiplex congenita

Previous genetic testing

Testing was performed with negative results including:

  • Chromosomal microarray
  • Whole exome sequencing

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 a homozygous, pathogenic, maternally and paternally inherited 13.13 kb deletion encompassing DOK7 exon 7.

Diagnosis: DOK7-related disorders

IGV view of DOK7 deletion

Uniform data from WGS clearly shows the single exon DOK7 deletion.

The Variantyx Difference

Why were these variants detected by IriSight® testing, and not detected by chromosomal microarray or exome testing?

  • The size of the 13.13 kb deletion falls below the cut-off value for CMA (~25 kb).

  • Exomes are typically unable to detect deletions smaller than 3 exons in size. The exome report specifically noted that CNV analysis was attempted using the sequencing data but could not be completed.

    Variantyx genome analysis has a detection range from 1bp to whole chromosomal events, easily detecting the single exon deletion.

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