Erroneous genetic sex determination of a newborn twin girl due to chimerism caused by foetal blood transfusion. A case report

• Published in: Hormone research Vol. 60; no. 3; p. 148
• Main Authors: Johannsen, T H, Lundsteen, C, Visfeldt, J, Schwartz, M, Petersen, B L, Byskov, A G, Müller, J
• Format: Journal Article
• Language: English
• Published: Switzerland 2003
• Subjects: Blood Cells; Blood Transfusion; Cell Line; Chimera; Diagnostic Errors; Female; Fetal Blood; Fibroblasts; Gonadal Dysgenesis - diagnosis; Gonadal Dysgenesis - surgery; Humans; Infant, Newborn; Karyotyping; Male; Ovariectomy; Sex Chromosome Aberrations; Sex Determination Processes; Skin - cytology; Twins; Unnecessary Procedures
• ISSN: 0301-0163
• DOI: 10.1159/000072527

We present a case of erroneous sex determination in a newborn twin girl (twin A) due to chimerism.
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.
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.
Twin A is a 46,XX female with a chimeric 46,XY blood cell line due to intrauterine transfusion from her twin brother.