MISSED BY OTHERS, DETECTED BY US
IriSight® Case Study
Clinical presentation
A primigravida underwent anatomy scans at 19, 25 and 29 weeks gestation with the following findings:
- Borderline/mild lateral cerebral ventriculomegaly
- Wide cranial sutures
- Flat face, midface retrusion
- Multicystic kidney dysplasia, renal hypoplasia/aplasia
- Hypospadias, micropenis
- Foot dorsiflexion, joint contracture
Previous genetic testing
Testing was performed with negative results including:
- 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 a paternally inherited, likely pathogenic 77.43 kb deletion encompassing FAT4 exons 3-4. Along with a second, maternally inherited, pathogenic c.5704C>T FAT4 variant.
A paternally inherited, pathogenic, intronic MYBPC3 variant was also identified.
Diagnosis: FAT4-related disorders, Hypertrophic cardiomyopathy 4
Uniform data from WGS clearly shows the paternally inherited partial FAT4 deletion (top) and the small sequence change (bottom). The MYBPC3 variant is not shown.
The Variantyx Difference
Why were these variants detected by IriSight® testing, and not detected by chromosomal microarray?
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While the size of the 77.48 kb deletion falls above the cut-off value for CMA (~25 kb), technical limitations specify that single gene partial copy number variants may not be detected. This variant only affects two exons of the FAT4 gene.
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CMA is unable to detect small sequence changes.
Variantyx genome analysis has a detection range from 1 bp to whole chromosomal events, easily detecting the copy number variant as well as both single nucleotide changes.
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