title: Discordant prenatal phenotype and karyotype of monozygotic twins characterized by the unequal distribution of two cell lines investigated by different methods: a review.
abstract: We present the case of a monozygotic twin pregnancy discordant for phenotype and karyotype. A chorionic villus sample was performed at the 11th week of gestation in a primigravida because of cystic hygroma detected by ultrasound in one twin of a monochorionic, biamniotic pregnancy. Rapid testing by means of quantitative fluorescence polymerase chain reaction and conventional karyotyping, obtained by both short- and long-term culture, revealed a homogeneous monosomy X (45,X). Amniocentesis was performed separately for both twins before termination and showed an homogeneous monosomy X in one sample and a 46,X,del(X)(p11.1) karyotype in the other one. Postmortem fetal tissues culture confirmed the discordant karyotype between the two embryos. Placental samples obtained after termination revealed the cell line which was not detected at chorionic villus sampling. Based on this and previous reports, we suggest 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.
authors.affiliation: Clinical Genetic Unit, Dipartimento Salute della Donna, del Bambino e del Neonato, Fondazione Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Gentilin
authors.forename: Silvana
authors.initials: S
authors.lastname: Guerneri
authors.forename: Vera
authors.initials: V
authors.lastname: Bianchi
authors.forename: Federica
authors.initials: F
authors.lastname: Natacci
authors.forename: Augusto
authors.initials: A
authors.lastname: Colombo
authors.forename: Roberto
authors.initials: R
authors.lastname: Fogliani
authors.forename: Renato
authors.initials: R
authors.lastname: Fortuna
authors.forename: Domenico A
authors.initials: DA
authors.lastname: Coviello
authors.forename: Cristina
authors.initials: C
authors.lastname: Curcio
authors.forename: Faustina
authors.initials: F
authors.lastname: Lalatta
mesh_terms: D000328:Adult; D002460:Cell Line; D015193:Chorionic Villi Sampling; D004200:Diseases in Twins / Q000151:congenital / Q000000981:diagnostic imaging / Q000235:genetics; D005260:Female; D006801:Humans; D007621:Karyotyping; D018191:Lymphangioma, Cystic / Q000151:congenital / Q000000981:diagnostic imaging / Q000235:genetics; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics*; D016216:Ultrasonography, Prenatal