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|LETTER TO EDITOR
|Year : 2002 | Volume
| Issue : 1 | Page : 71
Chromosome 19; 20 reciprocal translocation.
F Jayakaran, P Tilak, SM Rajangam, IM Thomas
Source of Support: None, Conflict of Interest: None
Keywords: Abortion, Habitual, genetics,Adult, Chromosomes, Human, Pair 19, genetics,Chromosomes, Human, Pair 20, genetics,Consanguinity, Female, Human, Karyotyping, Male, Spermatozoa, Translocation (Genetics),
|How to cite this article:|
Jayakaran F, Tilak P, Rajangam S M, Thomas I M. Chromosome 19; 20 reciprocal translocation. J Postgrad Med 2002;48:71
A couple, aged 26 and 34 years with third degree consanguineous marriage were referred for cytogenetic analysis and counseling for three pregnancy losses, a missed abortion, a blighted ovum diagnosed by ultrasound and yet another missed abortion.
Semen analysis showed a normal picture (count of 77.4 mill/ml, rapid linear motility 50-60%, normal morphology 82%). Chromosome analysis showed 46, XX in wife and 46, XY, t(19;20)(p13;p11) or 46,XY,t(19;20)(19qter->p13::20p11->20pter)(20qter->p11:19p13->pter) in husband.
Balanced reciprocal translocations are the largest group of chromosomal aberrations responsible for recurrent abortion in couples. The husband had a normal phenotype as his genotype had no genetic loss (balanced translocation). His semen analysis also appeared within the normal range. And yet the balanced translocation must have given rise to unbalanced gametes in the sperm resulting in 3 first trimester losses. That the translocation may be responsible for the pregnancy losses seems credible, even though little is known about the etiology of paternally derived chromosomal abnormalities. There is direct quantitative evidence that chromosomal breaks pre-exist in human sperm before fertilization. There is also no selection at fertilization against sperm carrying chromosomal abnormalities. The chromosomes most frequently involved in translocation are 4,7,9,11,18, 21 and 22. The 2 chromosomes involved here are 19 and 20, which have hitherto not been reported in literature, though there is one reportof a 46, XX,t(19;22)(p12;q22).
In this case, the husband may have had sperms with the translocation, leading to genetic imbalance and abortion. Coincidently, consanguinity, a known factor for an increased frequency of abortions, may have caused homozygosity of a recessive gene, resulting in abortions. The effect of consanguinity on reproduction is uncertain; it may cause bad obstetric history, though there are those who dispute its effect.
The couple was given genetic counseling. A recurrence risk figure (33%) was given for an unstable chromosomally abnormal fetus in subsequent pregnancies. The necessity of doing prenatal diagnosis in subsequent pregnancies, to detect either the translocation carrier status or the unbalanced chromosomal rearrangement in the fetus, was impressed upon the couple. If acceptable, donor sperm insemination may be an alternative possibility.
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