Monosomy X rescue explains discordant NIPT results and leads to uniparental isodisomy |
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| Authors: | M Katharine Rudd Justin B Schleede Sabrina R Williams Kristy Lee Jennifer Laffin Romela Pasion Peter R Papenhausen |
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| Institution: | 1. Center for Molecular Biology and Pathology, Laboratory Corporation of America Holdings, Research Triangle Park, NC, USA;2. Savannah Perinatology Associates, Memorial University Medical Center, Savannah, GA, USA;3. Wisconsin State Laboratory of Hygiene Clinical Genetics Laboratories, University of Wisconsin Madison, Madison, WI, USA |
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| 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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