Fetus Conceived via In Vitro Fertilization With Mosaic Uniparental Isodisomy and Two Balanced Translocations.

Area of Science:

• Human Genetics
• Reproductive Medicine
• Genomic Imprinting

Background:

• Balanced chromosomal translocations affect 0.14% of the population, increasing risks for genetic abnormalities like uniparental disomy (UPD) and mosaicism.
• Preimplantation genetic testing (PGT) aids in identifying some genetic disorders during in vitro fertilization (IVF).
• Specific translocations t(6;21) and t(5;15) have been individually documented but not concurrently in a viable fetus.

Observation:

• A couple, known carriers of distinct balanced translocations, conceived via IVF with normal PGT.
• Chorionic villus sampling (CVS) identified fetal inheritance of maternal t(6;21) and paternal t(5;15) translocations.
• Subsequent amniocentesis confirmed the translocations and revealed mosaic maternal uniparental isodisomy of chromosome 14 (UPD(14)mat).

Findings:

• The fetus presented a unique combination of two different balanced translocations inherited from each parent.
• The case documented mosaic maternal uniparental isodisomy of chromosome 14 (UPD(14)mat) alongside the translocations.
• The probability of a fetus inheriting both specific translocations was calculated at 2.8%.

Implications:

• This case underscores the complex interplay of imprinted genes leading to multiple, concurrent genetic alterations.
• It highlights potential inconsistencies and limitations of diagnostic methods like PGT, CVS, and amniocentesis in reproductive contexts.
• The extreme rarity of this genetic combination emphasizes the need for comprehensive genetic counseling before IVF conception in translocation carrier couples.