Sexual discordance in monozygotic twins

E. J. Perlman, Gail Stetten, C. M. Tuck-Muller, R. A. Farber, W. L. Neuman, K. J. Blakemore, G. M. Hutchins

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


We report on monozygotic (MZ) twins who were discordant for phenotypic sex and Ullrich-Turner syndrome (UTS). The nonviable female was hydropic with cystic hygromas, ventricular septal defect, bicuspid aortic valve, polysplenia, intestinal malrotation, and small ovaries. The male was phenotypically normal. The monochorionic, diamniotic placenta had hydropic changes limited to the UTS infant's side. Skin samples from the infants and blood from their parents were obtained for cytogenetic and molecular analysis. Karyotypes of the twins were 45,X and 46,XY. Quinacrine polymorphisms on 7 chromosomes and RFLP analysis at 8 loci showed complete identity. MZ twins discordant for phenotypic sex have been described previously. Most of these show evidence of mosaicism in a 45,X patient with a normal 46,XY cell line, and a normal 46,XY male. While the issue of mosaicism in our case cannot be fully resolved, no mosaicism was found in 50 cells analyzed cytogenetically from each culture or by PCR analysis of a Y-specific sequence. The twins probably originated from either postzygotic nondisjunction or anaphase lag, followed or accompanied by twinning. The discordant placental morphology suggests an embryonic origin of at least part of the placental mesenchymal core.

Original languageEnglish (US)
Pages (from-to)551-557
Number of pages7
JournalAmerican journal of medical genetics
Issue number4
StatePublished - 1990


  • Turner syndrome
  • monozygotic twins
  • placenta disease
  • polymorphism (genetics)

ASJC Scopus subject areas

  • Genetics(clinical)


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