title: Monozygotic twins discordant for 18q21.2qter deletion detected by array CGH in amniotic fluid.
abstract: Discordant chromosomal anomalies in monozygotic twins may be caused by various timing issues of erroneous mitosis and twinning events. Here, we report a prenatal diagnosis of heterokaryotypic monozygotic twins discordant for phenotype. In a 28-year-old woman, ultrasound examination performed at 26 weeks of gestation, detected intrauterine growth restriction and unilateral cleft lip and palate in twin B, whereas twin A had normal fluid, growth and anatomy. Molecular karyotyping in twin B identified a 18q21.2qter deletion, further confirmed by FISH analysis on amniocytes. Interestingly, in twin A, cytogenetic studies (FISH analysis and karyotype) on amniocytes were normal. Genotyping with microsatellite markers confirmed the monozygosity of the twins. At 32 weeks of gestation, selective termination of twin B was performed by umbilical cord coagulation and fetal blood samples were taken from the umbilical cord in both twins. FISH analyses detected mosaicism in both twins with 75% of cells being normal and 25% harboring the 18qter deletion. After genetic counseling, the parents elected to terminate the second twin at 36 weeks of gestation. In postmortem studies, FISH analyses revealed mosaicism on several tissues in both twins. Taking into account this observation, we discuss the difficulties of genetic counseling and management concerning heterokaryotypic monozygotic twins.
authors.affiliation: Service de Gynécologie-Obstétrique, Hôpital Necker-Enfants Malades, AP-HP, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Essaoui
authors.forename: M
authors.initials: M
authors.lastname: Nizon
authors.forename: M P
authors.initials: MP
authors.lastname: Beaujard
authors.forename: A
authors.initials: A
authors.lastname: Carrier
authors.forename: J
authors.initials: J
authors.lastname: Tantau
authors.forename: M C
authors.initials: MC
authors.lastname: de Blois
authors.forename: S
authors.initials: S
authors.lastname: Fontaine
authors.forename: C
authors.initials: C
authors.lastname: Michot
authors.forename: J
authors.initials: J
authors.lastname: Amiel
authors.forename: J P
authors.initials: JP
authors.lastname: Bernard
authors.forename: T
authors.initials: T
authors.lastname: Attié-Bitach
authors.forename: M
authors.initials: M
authors.lastname: Vekemans
authors.forename: C
authors.initials: C
authors.lastname: Turleau
authors.forename: Y
authors.initials: Y
authors.lastname: Ville
authors.forename: V
authors.initials: V
authors.lastname: Malan
mesh_terms: D000328:Adult; D000653:Amniotic Fluid; D002872:Chromosome Deletion; D025063:Chromosome Disorders / Q000175:diagnosis* / Q000235:genetics; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics*; D002972:Cleft Palate / Q000175:diagnosis / Q000235:genetics; D055028:Comparative Genomic Hybridization; D004200:Diseases in Twins / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D005317:Fetal Growth Retardation / Q000175:diagnosis / Q000235:genetics; D006801:Humans; D018895:Microsatellite Repeats; D009030:Mosaicism; D010641:Phenotype; D011247:Pregnancy; D011296:Prenatal Diagnosis; D014430:Twins, Monozygotic / Q000235:genetics*
keywords: Array CGH; Deletion 18q21.2qter; Monozygotic twins; TCF4 gene