Monosomy X rescue explains discordant NIPT results and leads to uniparental isodisomy

Prenatal Diagnosis
M Katharine RuddPeter R Papenhausen

Abstract

Noninvasive prenatal testing accurately detects trisomy for chromosomes 13, 21, and 18, but has a significantly lower positive predictive value for monosomy X. Discordant monosomy X results are often assumed to be due to maternal mosaicism, usually without maternal follow-up. We describe a case of monosomy X-positive noninvasive prenatal testing that was discordant with the 46,XX results from amniocentesis and postnatal testing. This monosomy X pregnancy doubled the single X chromosome, leading to 45,X/46,XX mosaicism in the placenta and uniparental isodisomy X in the amniotic fluid. Thus, at least some discordant monosomy X results are due to true mosaicism in the pregnancy, which has important implications for clinical outcome and patient counseling.

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Citations

Jul 13, 2021·Taiwanese Journal of Obstetrics & Gynecology·M Rosario Torres AguilarM Reyes Granell Escobar

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