ABSTRACT
Monozygotic twins discordant for trisomy 21 are rare. We present the twelfth reported case of this uncommon condition undergoing invasive prenatal diagnosis. Dealing with discordant fetal anomalies in monochorionic pregnancy can be challenging for physicians and patients; pros and cons of different invasive procedure options must be discussed with the couple, contending with certain specific peculiarities of this type of pregnancy. Although chorionic villi sampling can be performed earlier, higher risk of misdiagnosis of discordant aneuploidy is reported. Indeed, when heterokaryotic twins are suspected, a two-sampling amniocentesis is recommended, to ensure independent sampling of each fetus and to rule out confined placental mosaicism as well. The couple should be informed of the possible management and the risks for the non-affected twin whether selective reduction is required, and likewise if the pregnancy continues without selective termination.
Subject(s)
Down Syndrome , Female , Humans , Pregnancy , Down Syndrome/diagnosis , Karyotyping , Placenta , Prenatal Diagnosis/methods , Twins, MonozygoticABSTRACT
BACKGROUND: Monozygotic twins are nearly identical in genotype and phenotype because monozygotic twins arise from one fertilized oocyte. In all cases of discordant karyotype in monozygotic twins, trisomy 21 accounts for about one in 385,000. Monozygotic twins discordant for Robertsonian translocation trisomy 21 of the der (21;21)(q10;q10), in which the additional chromosome originates from the father is rare. CASE PRESENTATION: A 28-year-old parous woman, G3P1A0, came to our institution for a dating scan at 8 weeks of gestation. The transvaginal ultrasound examination demonstrated a monochorionic diamniotic pregnancy. She and her husband were healthy, with no family history of trisomy 21 or other congenital diseases. The ultrasound examination of nuchal translucency thickness was discordant in twins at 13 weeks (twin A, NT 1.4 mm with CRL being 65 mm; twin B, NT 7.8 mm with CRL being 69 mm). At 17+ 4 weeks, twin A was normal, but ventricular septal defect and the hypoplastic left heart was detected in twin B. The deepest vertical pocket was 18 mm in twin A (oligohydramnios) and 102 mm in Twin B (polyhydramnios). The bladder in twin A was absent. Ultrasound findings indicated TTTS Stage II. Amniocentesis was performed for the two fetuses. The karyotyping results revealed 46, XX in twin A but 46,XX,+ 21,der (21;21)(q10;q10) in twin B. For twin B, the parents opted for selective fetal termination by radiofrequency ablation. The procedure was uneventful. At 40+ 5 weeks, twin A was born with a birth weight of 4120 g by vaginal delivery. CONCLUSIONS: The early detection of discordant karyotype and twin-to-twin transfusion syndrome is beneficial to the early intervention. In monozygotic twins with a discordant anomaly, the discordant karyotype should be considered.
Subject(s)
Amniocentesis , Down Syndrome/genetics , Fetofetal Transfusion/genetics , Pregnancy, Twin/genetics , Twins, Monozygotic/genetics , Adult , Chromosomes, Human, Pair 21/genetics , Down Syndrome/diagnosis , Female , Fetofetal Transfusion/diagnosis , Humans , Infant, Newborn , Karyotyping , Nuchal Translucency Measurement , Oligohydramnios , Pregnancy , Pregnancy Reduction, Multifetal , Ultrasonography, PrenatalABSTRACT
Monochorionic-diamniotic twins are usually monozygotic twins and known to be associated with adverse obstetric and perinatal outcomes. Cases of discordant karyotype of monozygotic twins are rare and most involves sex chromosomes. We present the first case of monochorionic twins with discordant karyotype manifested as mosaic trisomy 14 in one twin (B) and a normal karyotype in the other (A). We describe the postmortem pathological and imaging findings of the trisomic twin and for the first time neuropathological findings of this entity. Metaphase chromosome analysis of twin B using fetal tissue showed a 47,XX, +14 karyotype. Chromosomal microarray analysis (CMA) using fetal tissue revealed 38% mosaicism. CMA with placental tissue from both sides demonstrated normal karyotype and confirmed monozygosity, highlighting the value of array based testing on diagnosing mosaicism and zygosity.
Subject(s)
Trisomy/diagnosis , Trisomy/genetics , Twins, Monozygotic , Alleles , Autopsy , Chromosomes, Human, Pair 14/genetics , Comparative Genomic Hybridization , Fatal Outcome , Female , Genotype , Humans , Karyotyping , Magnetic Resonance Imaging , Mosaicism , Polymorphism, Single Nucleotide , Ultrasonography, PrenatalABSTRACT
Monochorionic twins with discordant karyotypes are rare and mostly caused by post-zygotic mitotic nondisjunction. A 32 year old nulliparous woman at 11 weeks of gestation with spontaneous twin pregnancy was referred to our hospital. An amniocentesis was performed in both amniotic sacs at 15 weeks of pregnancy. One fetus in monochorionic twin pregnancy was diagnosed with Turner syndrome with cystic hygroma, and the other fetus was normal. Because of high mortality rate in abnormal fetuses, the umbilical cord coagulation was performed using radiofrequency ablation to prevent the damage of co-twin that may be caused by the demise of one fetus. After delivery, chorionicity of placenta was ascertained by pathologic exam. Postnatal findings of physical exam, abdominal and brain sonography were normal in the surviving neonate.
