Monochorionic dizygotic twins with discordant sex and confined blood chimerism.
Monochorionic (MC) pregnancy in humans is usually considered to be associated only with monozygotic twinning. However, several reports have revealed that dizygotic (DZ) twins can also share a chorion during pregnancy. A chimera is defined as an organism that contains different cells derived from two or more distinct zygotes. As artificial reproductive techniques develop, it can be predicted that the occurrence of MC DZ twins will increase, and DNA-fingerprinting methods, such as short tandem repeat (STR) analysis, will be essential for their accurate diagnosis. We report the first Korean case of MC DZ twins with blood chimerism, 46,XX/46,XY, as a consequence of in vitro fertilization/embryo transfer. The clinical phenotypes of the twins' genitalia were complete female and male, respectively. Monochorionicity was confirmed by pathological analysis of the placenta after delivery. The dizygosity and confined blood chimerism of the twins were confirmed by STR analysis using their peripheral lymphocytes and skin fibroblasts. The confined blood chimerism of the twins can be considered similar to the status of the hematopoietic system in patients after allogenic bone marrow transplantation.


CONCLUSIONS
When MC twins with discordant sex are expected during pregnancy, it is important to consider the possibility of DZ twins showing normal sexual development, especially in twins who were fertilized using artificial reproductive techniques.
Department of Pediatrics, Seoul National University Children's Hospital, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul, 110-769, South Korea, litdino@naver.com.
Hye Jin
HJ
Lee
Sung Chul
SC
Yoon
Jung Min
JM
Ko
Moon Woo
MW
Seong
Sung Sup
SS
Park
Jin Sun
JS
Choi
Sun Kyung
SK
Oh
D000328:Adult; D046528:Chimerism; D002823:Chorion / Q000098:blood supply*; D004624:Embryo Transfer / Q000009:adverse effects*; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D010920:Placenta / Q000098:blood supply; D011247:Pregnancy; D059285:Pregnancy, Twin; D014429:Twins, Dizygotic / Q000235:genetics*; D016216:Ultrasonography, Prenatal