title: Erroneous genetic sex determination of a newborn twin girl due to chimerism caused by foetal blood transfusion. A case report.
abstract: OBJECTIVE
  We present a case of erroneous sex determination in a newborn twin girl (twin A) due to chimerism.
  
  
  METHODS
  Amniocentesis and ultrasound examination had pointed towards male sex of both twins. At birth, twin A presented as a phenotypically normal female with 46,XY karyotype, and 46,XY gonadal dysgenesis was suspected. Twin B was a normal male.
  
  
  RESULTS
  In our department, further examinations of twin A included undetectable testosterone and inhibin-B and elevated FSH. Ultrasound suspected an infantile uterus, and sequencing of the SRY gene was normal. After gonadectomy, a 46,XX karyotype was demonstrated in both normal infantile ovaries and in the fibroblasts from a skin biopsy. Analysis of X-linked markers in DNA from blood lymphocytes in both twins was identical, consistent with 46,XY karyotypes.
  
  
  CONCLUSIONS
  Twin A is a 46,XX female with a chimeric 46,XY blood cell line due to intrauterine transfusion from her twin brother.
authors.affiliation: Department of Growth and Reproduction, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. trinejohannsen@rh.dk
authors.forename: T H
authors.initials: TH
authors.lastname: Johannsen
authors.forename: C
authors.initials: C
authors.lastname: Lundsteen
authors.forename: J
authors.initials: J
authors.lastname: Visfeldt
authors.forename: M
authors.initials: M
authors.lastname: Schwartz
authors.forename: B L
authors.initials: BL
authors.lastname: Petersen
authors.forename: A G
authors.initials: AG
authors.lastname: Byskov
authors.forename: J
authors.initials: J
authors.lastname: Müller
mesh_terms: D001773:Blood Cells; D001803:Blood Transfusion; D002460:Cell Line; D002678:Chimera; D003951:Diagnostic Errors; D005260:Female; D005312:Fetal Blood; D005347:Fibroblasts; D006059:Gonadal Dysgenesis / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D008297:Male; D010052:Ovariectomy; D012729:Sex Chromosome Aberrations; D019849:Sex Determination Processes; D012867:Skin / Q000166:cytology; D014427:Twins; D019564:Unnecessary Procedures