title: Klinefelter twins presenting with discordant aneuploidies, acardia, forked umbilical cord and with different gonadal sex despite monozygosity.
abstract: OBJECTIVE
  A higher frequency of twin births in sibships of Klinefelter syndrome patients and also monozygotic or dizygotic twins, themselves being affected by Klinefelter syndrome have been noted repeatedly. To address this issue, we evaluated type and frequency of twinning among Klinefelter fetuses that we had received for autopsy within a 'Prenatal Diagnosis' program.
  
  
  METHODS
  We performed fetal autopsies, and genetic analyses on DNA extracted from stained histological slides.
  
  
  RESULTS
  Among 41 prenatal diagnoses of a 47, XXY karyotype we observed four twin pairs. One was dizygotic with discordant Klinefelter and Down syndrome. Three twin pairs were monozygotic as concluded from monochorial placentation. In two monozygotic pairs one twin partner was an acardiac monster and in one of these the acardiac twin showed a female gonadal sex and missing Y-chromosomal SRY-sequences as confirmed by polymerase chain reaction.
  
  
  CONCLUSIONS
  There is a high rate of twinning and twin reversed arterial perfusion sequence among our Klinefelter fetuses. Forked umbilical cords at the placental insertion site in one case allowed classification as conjoined twins in the sense of a 'funiculopagus'. Anaphase lagging or semidizygosity by second polar body twinning are proposed as explanations for the gonadal sex discordance and the excessive developmental disadvantage in the one acardiac. Problems may arise with regard to non-invasive prenatal diagnosis of aneuploidies in twin pregnancies.
authors.affiliation: Institute of Medical Genetics, Medical University Vienna, Austria. helga.rehder@meduniwien.ac.at
authors.forename: Helga
authors.initials: H
authors.lastname: Rehder
authors.forename: Katharina
authors.initials: K
authors.lastname: Schoner
authors.forename: Britta
authors.initials: B
authors.lastname: Kluge
authors.forename: Frank
authors.initials: F
authors.lastname: Louwen
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schwinger
authors.forename: Juergen
authors.initials: J
authors.lastname: Neesen
mesh_terms: D000015:Abnormalities, Multiple / Q000175:diagnosis* / Q000235:genetics; D000328:Adult; D000649:Amniocentesis / Q000379:methods; D000782:Aneuploidy; D003937:Diagnosis, Differential; D004200:Diseases in Twins / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D005838:Genotype; D006330:Heart Defects, Congenital / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D007713:Klinefelter Syndrome / Q000175:diagnosis* / Q000235:genetics; D008297:Male; D012729:Sex Chromosome Aberrations; D014427:Twins; D014430:Twins, Monozygotic / Q000235:genetics; D014470:Umbilical Cord / Q000002:abnormalities*