Trisomy 8 mosaicism with pyloric atresia and situs ambiguous

Prenatal diagnosis of trisomy 8 mosaicism, initially identified by cffDNA screening

BACKGROUND

So called cell-free fetal DNA (cffDNA) in the maternal plasma, which is derived from placenta, is widely used to screen fetal aneuploidies, including trisomy 21, 18, 13 and sex chromosomes. Here we reported a case of trisomy 8 mosaicism (T8M), which was initially identified via cffDNA screening in noninvasive prenatal testing (NIPT).

METHODS

A 35-year-old woman received cffDNA screening at 17th week of gestation. Amniocentesis was performed subsequently, and karyotyping, single-nucleotide polymorphism array (SNP-array) and BACs-on-Beads™ (BoBs™) were used to determine fetal chromosome content. Interphase fluorescence in situ hybridization (FISH) was applied to determine the copy number of chromosome 8.

RESULTS

An enhanced risk for fetal trisomy 8 was identified by cffDNA screening in the studied pregnant woman. After amniocentesis trisomy 8 was found in 1 of 73 metaphases. SNP-array on DNA derived from cultured amniocytes and neonatal cord blood cells suggested the presence of T8M. Interphase FISH on native neonatal cord blood cells confirmed T8M with a percentage of 10%. The Bobs™ fluorescence data also suggested that 8q23-8q24 was amplified.

CONCLUSIONS

The current study shows that NIPT is suited to provide hints on rare autosomal trisomies, which have to be further validated and confirmed by other approaches.

Trisomy 8 mosaicism in the placenta: A Danish cohort study of 37 cases and a literature review

OBJECTIVE

To evaluate the risk of fetal involvement when trisomy 8 mosaicism (T8M) is detected in chorionic villus samples (CVS).

METHODS

A retrospective descriptive study of registered pregnancies in Denmark with T8M in CVS identified through a database search and a review of published cases of T8M found through a systematic literature search and inclusion of cross references. Pregnancies with T8M in CVS and no additional numerical chromosomal aberrations were included.

RESULTS

A total of 37 Danish cases and 60 published cases were included. T8M detected in a CVS was associated with fetal involvement in 18 out of 97 pregnancies (18.6% [95%CI: 11.4-27.7]). Eight out of 70 (11.4% [95%CI: 5.1-21.3]) interpreted prenatally to be confined placental mosaicism (CPM) were subsequently found to be true fetal mosaicisms (TFM).

CONCLUSION

T8M detected in CVS poses a significant risk of fetal involvement, and examination of amniotic fluid (AF) and/or fetal tissue should be offered. However, a normal result of AF still has a considerable residual risk of fetal involvement. Genetic counselling at an early gestational age is essential, and follow-up ultrasonography should be performed to predict fetal involvement if possible.

Bilateral severe microphthalmia in a neonate with trisomy 8 mosaicism: A new finding

Mosaic Trisomy 8 is a rare chromosomal abnormality estimated to occur one in 30,000 newborns. The phenotype is highly variable and the severity does not appear to be correlated with the proportion of cells that contain the additional chromosome. Ocular involvement in Trisomy 8 mosaicism has previously been described to include corneal opacities, retinal dystrophy, coloboma, and unilateral microphthalmia. We report a case of severe bilateral microphthalmia in a neonate with Trisomy 8 mosaicism, a previously unrecognized ophthalmic manifestation.

Prenatal detection of trisomy 8 mosaicism: Pregnancy outcome and follow up of a series of 17 consecutive cases

OBJECTIVE

To study the outcome of a series of individuals with prenatal detection of trisomy 8 mosaicism by chorionic villus sampling (CVS) and/or amniocentesis.

STUDY DESIGN

The databases of two Italian genetics units were reviewed to identify all consultations requested during pregnancy because of trisomy 8 mosaicism. To evaluate the pregnancy outcome, the regional registry of congenital malformations (including terminations of pregnancies) was consulted; additional follow-up data were collected by a telephone interview. The following outcomes were analysed: delivery, pre- and post-natal growth, psychomotor development, major malformations, other diseases/complications.

RESULTS

A total of 17 consecutive cases of trisomy 8 mosaicism were identified. Fourteen cases were first detected among women undergoing prenatal diagnosis by CVS; the remaining ones were identified among women who underwent amniocentesis. In most cases diagnosed by CVS, the chromosomal anomaly was only detected in long-term cell cultures (10/14) and was not confirmed by amniocentesis (11/13). There were two terminations of pregnancy and 15 live births; no major birth defects were observed among live born infants and only a case with prenatal and postnatal growth retardation was observed (mean age at follow-up interview was 5.9 years).

CONCLUSION

Our data showed an overall positive prognosis for cases with an apparent confined placental mosaicism and those with low-level mosaicism in amniotic fluid if no congenital anomalies were detected by foetal ultrasound examinations. However, larger studies are warranted to better define the associated risk of neurodevelopmental anomalies.