Sex-Discordant Monochorionic Dizygotic Twins After Double Blastocyst Transfer: Blood Chimerism Demonstrated by Multimodal Genetic Testing.
Kotaro Yuki, Yumiko Taura, Hiroki Morishita et al.
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Case in brief
A 38-year-old woman conceived through intracytoplasmic sperm injection and double blastocyst transfer, leading to monochorionic diamniotic twins. At 21 weeks, discordant external genitalia were noted. The delivery resulted in a phenotypically normal female and male infant. Genetic testing revealed mixed 46,XX/46,XY cell lines in peripheral blood, indicating predominantly blood-limited chimerism, consistent with monochorionic dizygotic twinning.
What made this case unusual
The case presents a rare instance of monochorionic dizygotic twins with blood chimerism, demonstrated through comprehensive genetic testing, which is atypical for this type of twinning.
Diagnostic / clinical pearl
Clinicians should consider the possibility of blood chimerism in cases of discordant genitalia in monochorionic twins, as genetic testing can reveal complex underlying mechanisms.
Why it matters
This case underscores the importance of integrating genetic findings with clinical assessments to better understand the implications of chimerism in twin pregnancies.