| A Case of (21q 21q) Translocation Down Syndrome Inherited from a t(21q 21q) Balanced Carrier Mother. |
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Byeong Gie Yeo1, Chong Woo Bae1, Yong Mook Choi1, Chang Il Ahn1, Bo Hoon Oh2 |
1Department of Pediatrics, College of Medicine, Kyung Hee University, Seoul, Korea
2Department of Obstetrics & Gynecology, College of Medicine, Kyung Hee University, Seoul, Korea |
| 균형 전좌형 보인자 모에서 출생한 (21q 21q)
전좌형 Down 증후군 1례 |
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여병기1, 배종우1, 최용묵1, 안창일1, 오보훈2 |
1경희대학교 의과대학 소아과학교실
2경희대학교 의과대학 산부인과학교실 |
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Received: 28 December 1989 • Accepted: 21 March 1990 |
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| Abstract |
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Vast majority of t(21q 21q) Down syndrome occur de novo and familial cases are extremely rare.
In familial translocation Down syndrome, One of the parent show 45 chromosomes.
In general, the carrier parent carrying (21q 21q) translocation is phenotypically normal because
significant amount of genetic material has not been lost in the translocation process. Homologous
Robertsonian translocation can be produced either by abnormal gametogenesis or by postzygotic
mistake in mitosis soon after fertilization. The incidence of t (21q 21q) balanced carrier in general
population is 1 in 2 — 2.5 million live birth.
In homologous Robertsonian translocation, the risk of producing abnormal offspring is 100%.
Therefore, this carrier mother should be informed about sterilization.
In the present case, chromosomal study of mother showing normal female phenotype revealed
balanced (21q 21q) translocation carrier with a karyotype 45, XX, —21, —21, +t (21q 21q) and
chromosomal study of patient revealed (21q 21q) translocation down syndrome with a karyotype 46,
XY, -21, +t (21q 21q).
Thus, it is important to perform maternal chromosome study in case of translocation down
syndrome and genetic counselling of this pedigree to prevent producing repetitive abnormal off-
springs.
In addition to case report, we present a brief review of the related literatures. |
| Key Words:
Down syndrome, Translocation, Chromosome anomaly |
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