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Monochorionic-diamniotic twins discordant in gender from a naturally conceived pregnancy through postzygotic sex chromosome loss in a 47,XXY zygote


Zech, N H; Wisser, J; Natalucci, G; Riegel, M; Baumer, A; Schinzel, A (2008). Monochorionic-diamniotic twins discordant in gender from a naturally conceived pregnancy through postzygotic sex chromosome loss in a 47,XXY zygote. Prenatal Diagnosis, 28(8):759-763.

Abstract

OBJECTIVE: It is generally believed that monochorionic-diamniotic twin pregnancies result from one fertilized oocyte with both siblings having the same genotype and phenotype. In rare instances, due to somatic mutations or chromosome aberrations, the karyotypes and phenotypes of the two twins can differ. METHOD: We report cytogenetic, molecular genetic and clinical examinations in monochorionic-diamniotic twins discordant in gender. RESULTS: The monochorionic-diamniotic status of the twins was diagnosed by ultrasound and histologic examination of the placenta. Prenatal chromosome examination performed on amniocytes revealed a normal female karyotype in one and a 46,XX(26)/46,XY(3) karyotype in the other twin. Molecular examinations confirmed monozygosity despite discordant sex. Based on the cytogenetic and molecular results of lymphocytes and placental cells, the only explanation for gender discordance was that the conceptus originally had a 47,XXY chromosome complement. CONCLUSION: A 47,XXY zygote appears to have undergone a twinning process. A postzygotic loss of the X chromosome in some cells and the Y chromosome in other cells, either before or after twinning, resulted in 46,XX/46,XY mosaicism in both monozygotic (MZ) twins. The sex discordance of the MZ twins can be explained by different proportions of the 46,XX and 46,XY cell lines in the gonads and other tissues.

OBJECTIVE: It is generally believed that monochorionic-diamniotic twin pregnancies result from one fertilized oocyte with both siblings having the same genotype and phenotype. In rare instances, due to somatic mutations or chromosome aberrations, the karyotypes and phenotypes of the two twins can differ. METHOD: We report cytogenetic, molecular genetic and clinical examinations in monochorionic-diamniotic twins discordant in gender. RESULTS: The monochorionic-diamniotic status of the twins was diagnosed by ultrasound and histologic examination of the placenta. Prenatal chromosome examination performed on amniocytes revealed a normal female karyotype in one and a 46,XX(26)/46,XY(3) karyotype in the other twin. Molecular examinations confirmed monozygosity despite discordant sex. Based on the cytogenetic and molecular results of lymphocytes and placental cells, the only explanation for gender discordance was that the conceptus originally had a 47,XXY chromosome complement. CONCLUSION: A 47,XXY zygote appears to have undergone a twinning process. A postzygotic loss of the X chromosome in some cells and the Y chromosome in other cells, either before or after twinning, resulted in 46,XX/46,XY mosaicism in both monozygotic (MZ) twins. The sex discordance of the MZ twins can be explained by different proportions of the 46,XX and 46,XY cell lines in the gonads and other tissues.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Medical Genetics
04 Faculty of Medicine > University Hospital Zurich > Clinic for Obstetrics
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2008
Deposited On:11 Dec 2008 10:35
Last Modified:05 Apr 2016 12:37
Publisher:Wiley-Blackwell
ISSN:0197-3851
Publisher DOI:10.1002/pd.2031
PubMed ID:18567067
Permanent URL: http://doi.org/10.5167/uzh-6422

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