Medicover Genetics publishes first report of tissue-specific genetic analysis and genotype–phenotype correlation in child with mosaic trisomy 18

Medicover Genetics Editorial Team|

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Medicover Genetics is pleased to announce the publication of a letter to the editor in the Journal of Perinatal Medicine co-authored by several members of the Medicover Genetics team. The letter documents for the first time a child with mosaic trisomy 18 with an organ/tissue-specific genetic analysis of genotype–phenotype correlation, and asks whether tissue-specific genetic analyses in cases of trisomy 18 mosaicism can predict postnatal outcome.

The letter presents a case report of a pregnant woman with an initial low risk for trisomy 18 in a female foetus as determined by NIPT (non-invasive prenatal test). Subsequent ultrasound identified a male foetus, and a repeat NIPT revealed a high risk of trisomy before amniocentesis confirmed mosaic trisomy 18. After birth, the male infant had a heart defect that was corrected surgically but no other health conditions.

The authors analysed tissue samples from all three germ layers using conventional chromosome analysis and . They detected mosaicism for a free trisomy 18 in all analysed tissues, with a high-level of mosaic trisomy 18 (96%) in heart muscle tissue and a low level (between 1% and 10%) in all other tissues. This finding matched with the child’s phenotype.

The article continues with a valuable discussion about the implications of these findings and the acknowledgment that neither the level of mosaic trisomy 18 in amniotic fluid, nor a prenatal ultrasound can predict the risk for postnatal neurocognitive impairment. The authors hypothesize that for mosaic trisomy 18, a prenatal central-nervous system-specific genetic analysis may provide some answers, but summarize that there is “currently no way to prenatally provide prognostically reliable information about the severity of morbidity, in particular of neurocognitive impairment.”

Read the full article .

Last updated: June 8, 2026

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