The identification of a spontaneous 47, XX, +21/46, XY chimeric fetus with male genitalia
1 Laboratory for Cytogenetics, Center for Genetic Counseling, Buddhist Tzu Chi General Hospital, 707, Sec 3, Chunyang Rd, Hualien, 970, Taiwan
2 Graduate Institute of Medical Sciences, Tzu Chi University, Hualien County, 970, Taiwan
3 Department of Obstetrics & Gynecology, Buddhist Tzu Chi General Hospital, Dalin Branch, Chiayi County, 622, Taiwan
4 Department of Medical Laboratory Science and Biotechnology, National Cheng Kung University, 1, University Road, Tainan City, 701, Taiwan
5 Department of Urology, Buddhist Tzu Chi General Hospital, 707, Sec 3, Chunyang Rd, Hualien County, 970, Taiwan
6 Department of Molecular Biology and Human Genetics, Tzu Chi University, 701, Sec 3, Chunyang Rd, Hualien, 970, Taiwan
BMC Medical Genetics 2012, 13:85 doi:10.1186/1471-2350-13-85Published: 20 September 2012
Approximately 30 sex-chromosome discordant chimera cases have been reported to date, of which only four cases carried trisomy 21. Here, we present an additional case, an aborted fetus with a karyotype of 47,XX, +21/46,XY.
Autopsy demonstrated that this fetus was normally developed and had male genitalia. Major characteristics of Down syndrome were not observed except an enlarged gap between the first and second toes. Karyotyping of tissues cultured from the fetus revealed the same chimeric chromosomal composition detected in the amniotic fluid but with a different ratio of [47,XX,+21] to [46,XY]. Further short tandem repeat analysis indicated a double paternal contribution and single maternal contribution to the fetus, with the additional chromosome 21 in the [47,XX,+21] cell lineage originating from the paternal side.
We thus propose that this chimeric fetus was formed via the dispermic fertilization of a parthenogenetic ovum with one (Y) sperm and one (X,+21) sperm.