Monochorionic twins discordant for mosaic trisomy 14

Area of Science:

• Reproductive Medicine
• Genetics
• Perinatology

Background:

• Monochorionic-diamniotic twins, typically monozygotic, face higher risks of adverse obstetric and perinatal outcomes.
• Discordant karyotypes in monozygotic twins are rare, predominantly involving sex chromosomes.

Observation:

• Presents the first documented case of monochorionic twins exhibiting a discordant karyotype.
• One twin (B) presented with mosaic trisomy 14, while the co-twin (A) had a normal karyotype.

Findings:

• Postmortem pathological and imaging findings of the trisomic twin are detailed, including novel neuropathological data.
• Metaphase chromosome analysis of twin B revealed a 47,XX,+14 karyotype with 38% mosaicism via chromosomal microarray analysis (CMA).
• CMA on placental tissue confirmed monozygosity and normal karyotype in twin A, underscoring CMA's diagnostic value for mosaicism and zygosity.

Implications:

• This case highlights the importance of advanced genetic testing, like CMA, in diagnosing rare conditions like twin mosaicism.
• Findings contribute to understanding the pathology and potential outcomes associated with mosaic trisomy 14 in a monochorionic twin setting.
• Provides critical data for genetic counseling and management strategies for discordant monozygotic twins.