Prenatal diagnosis of heterokaryotypic mosaic twins discordant for fetal sex

  title={Prenatal diagnosis of heterokaryotypic mosaic twins discordant for fetal sex},
  author={O. Schmid and Udo Trautmann and Hanan Jameel Ashour and Renate Ulmer and Rudolf A. Pfeiffer and Ernst Beinder},
  journal={Prenatal Diagnosis},
The presence of a monozygotic twin gestation with discordant sex of the twins is a very rare constellation, which is referred to as heterokaryotypic monozygotic pregnancy. This constellation can develop either due to a chromosomal aberration after twinning or is — as in the following case — due to a mitotic error before twinning and an unequal distribution of mosaicism in both embryos. So far the diagnosis of heterokaryotypic monozygotic pregnancy has always been made postnatally, with only one… 

Growth of heterokaryotic monozygotic twins discordant for Ullrich–Turner syndrome during the first years of life

The differences of heterokaryotic MZ Turkish twins who are discordant for Ullrich–Turner syndrome are reported on, with special interest on the spontaneous and growth hormone induced growth of the twins.

Monozygotic twins concordant for blood karyotype, but phenotypically discordant: A case of “mosaic chimerism”

It is suggested that blood is particularly unsuitable for cytogenetic investigations of twins, as shown by twin‐to‐twin transfusion syndrome observed during fetal life of the authors' twins.

Monozygotic twins with discordant karyotypes following preimplantation genetic screening and single embryo transfer: case report

The discordance in the twins’ karyotypes originated from a mosaic embryo that split probably due to apoptotic process in an early stage of embryo development, one of the possible mechanisms which can explain the embryo twinning process globally.

Prenatal diagnosis of female monozygotic twins discordant for Turner syndrome: implications for prenatal genetic counselling

It is suggested that, in cases of prenatal diagnosis of MZ female twins discordant for TS, the phenotype of each twin would be better predicted from karyotype analysis of cells from amniotic fluid than from fetal blood.

Discordant Prenatal Phenotype and Karyotype of Monozygotic Twins Characterized by the Unequal Distribution of Two Cell Lines Investigated by Different Methods: A Review

It is suggested that in cases of a phenotypic discordance detected at ultrasound in the first trimester, it is advisable to perform a karyotype analysis on amniocytes because it better reflects fetal constitution rather than chorionic villi or lymphocytes in case of heterokaryotipic monosomy X monochorionic twins.


The difficult diagnosis and management of a monochorionic twin pregnancy with discordant fetal sex is shown.

Heterokaryotypic Pregnancy: Monozygotic Monochorionic Twins Discordant for Trisomy 13

This report adds to the literature the second known case of a spontaneously conceived monochorionic twin pregnancy discordant for trisomy 13 and highlights the necessity of sampling both fetuses in cases of monoch orionic twins presenting with discordant structural anomalies.

Gender-Discordant Monochorionic-Diamniotic Twins Both With 45,X/46,X, Idic(Y) Mosaicism and a Novel Deletion Within the TBC1D5 Gene

  • A. InamdarMichael DiamondW. Shertz
  • Medicine, Biology
    Pediatric and developmental pathology : the official journal of the Society for Pediatric Pathology and the Paediatric Pathology Society
  • 2020
The case findings not only report Turner syndrome mosaicism with a novel genetic mutation but also stress the importance of clinical follow-up of twins in order to evaluate the functional abnormalities associated with isodicentric Y chromosomes including germ cell tumors.

Chimerism in twins: Caution is needed in interpretation of karyotypes

A case of suspected monozygotic twins with discrepant sex phenotype at birth, whereas the amniocentesis and the ultrasound examination had pointed towards male sex of both twins, which was in fact a 46,XX female with a chimeric 46,XY blood cell line due to intrauterine transfusion from her twin brother.



Sexual discordance in monozygotic twins.

The discordant placental morphology suggests an embryonic origin of at least part of the placental mesenchymal core and probably originated from either postzygotic nondisjunction or anaphase lag, followed or accompanied by twinning.

Monozygotic twins with 45,X/46,XY mosaicism discordant for phenotypic sex.

Two sets of monozygotic twins discordant for phenotypic sex ascertained at birth when the female twin was noted to have signs of the Ullrich-Turner syndrome are reported on.

Fetal blood sampling demonstrating chimerism in monozygotic twins discordant for sex and tissue karyotype (46,XY and 45,X)

A case of identical (monozygotic) twins with sex discordance, which on ultrasound evaluation revealed hydrops fetalis in one twin and a normal second twin, and the probable occurrence of post‐zygotic chromosomal non‐disjunction leading to the discordancy of the sex.

Monozygotic twins with discordant sex.

A nine-year-old girl with short stature was referred to the department of pediatrics at Kyushu University; karyotypic analysis performed on peripheral blood, using GTG techniques, demonstrated a 45,X/47,XYY mosaicism; the most plausible explanation was nondisjunction of the Y in the first cleavage division of the 46,XY zygote.

Monozygotic twins of discordant sex both with 45,X/46,X,idic(Y) mosaicism.

The occurrence of discordant phenotypic sex in monozygotic twins, involving gonadal dysgenesis with an abnormal dicentric Y, which presumably occurred de novo, followed by anaphase lag probably before the occurrence of twinning is documents.

Differentiation of Monochorionic and Dichorionic Twin Placentas by Antenatal Ultrasonic Evaluation

It is shown that ultrasound is reasonably accurate at identification of dichorionic from monochorionic twins (70% of monozygotic twins) by assessment of the thickness of the septum between the 2 gestational sacs, which indicates immediate delivery of the second twin if this condition is diagnosed antenatally by ultrasound.

The phenotype of 45,X/46,XY mosaicism: an analysis of 92 prenatally diagnosed cases.

It is concluded that 95% of 45,X/46,XY fetuses will have normal male genitalia, although there will also be a significant risk for abnormal gonadal histology, and long-term follow-up studies are needed to study, without ascertainment bias, stature, pubertal development, tumor risk, and fertility.

Discordant sex in one of three monozygotic triplets.

It is suggested that mitotic non-disjunction or anaphase lag occurring early during embryonic development accounted for the occurrence of monosomy X in one cell line of the affected triplet.

Prenatal diagnosis of 45,X/46,XY mosaicism—A review and update

  • L. Hsu
  • Medicine
    Prenatal diagnosis
  • 1989
This review shows a major difference in the phenotypic outcome between postnatal diagnosis and prenatal diagnosis and calls for collection of more data on 45,X/46,XY mosaicism diagnosed prenatally, more long‐term follow‐up of liveborn infants, and pathological studies of all abortuses.