Re: ULTRASOUND digest 1595
From: James S Smeltzer MD (gaperina@mindspring.com)
Wed May 8 22:37:52 2002
Although Dr. Benirshke has the last word on placentation and I have heard
of a Turners/Male twin discordant sex mosaic, I would think Klinefelter's
and normal female would be more frequent as Turner's is usually lethal in
the embryonic/fetal period. A DNA fingerprint will show unusual homology if
this is the case.
Jim Smeltzer
At 02:36 PM 5/7/2002 -0500, you wrote:
>This might be a case which might give you some clues for your question
>and I 'd like to share it with you.
>Since I was quite puzzled from a case of monochorionic twins I thought
>of writing to Prof Bernischke and asked his opinion. I scanned a
>patient at 8+4 weeks with the following findings: two amniotic sacs, two
>yalk sacs in a common extracelomic space. I actually used the pictures
>to demonstrate a monochorionic pregnancy in a couple of talks I
>gave on early scanning in twin pregnancy: I thought that these findings
>are proof of a monochorionic that means also monozygotic twin pregnancy.
>You cannot imagine my surprise when at 20 weeks I found that the twins
>were incontrovertibly discordant for the gender.
>What is the biological explanation for that? Is it possible that
>identical twins are only discordant in the phenotypus? Do dizygotic
>twins have only one
>extracelomic space?
>Answer:
>
>Dear Dr. Moroder:
>This set of twins is VERY unusual, as you correctly interpreted. The
>fact that they are of different gender is perhaps significant, but not
>necessarily
>PROOF that they are dizygotic. There are numerous cases described where
>a set of monozygotic twins were discordant for sex chromosome, where one
>baby is 46XY, the other 45XO. During early embryogenesis a Y-chromosome
>got lost and the other twin develops as a Turner's syndrome. When they
>are monochorionic, they often then also have blood chimerism, but that
>does not always happen. That is the first possibility - socalled
>heterokaryotypic
>twins (p. 846 in my book:Pathology of Human Placenta, Springer-Verlag,
>2000, 4th edition).
>But it is also true that VERY few dizygotic twins developed in a single
>chorionic sac and result then in blood chimerism. In fact, a rare case
>has even
>developed the transfusion syndrome, but only 4-5 cases are known to me
>that can be seen to be PROVEN. In fact, the first good case (color
>picture in
>the first edition of my book) was from Cameron in England and he
>subsequently showed that the twins (dichorionic though they were and
>chimeric)
>had been identical twins with anastomosis.
>I recommend that you wait until the twins are born and do karyotypes on
>them. I would be inclined to anticipate Turner in one.
>I hope this clarifies the situation.
>You should know though that in marmoset monkeys this is the REGULKAR
>mode of placentation and it occurs in cattle and a few other ungulates
>as
>well.
>Mit besten Gruessen, K. Benirschke
>
>Kurt Benirschke, M.D.
>Home: 8457 Prestwick Drive, La Jolla, CA 92037 Tel: 858-459-9132. FAX:
>858-459-1063.
>Office: UCSD Medical Center, 200 West Arbor Drive, San Diego, CA
>92103-8321. Tel.: 619-543-2618; Office(Agnes):619-543-5719. Fax:
>619-543-7711.e-mail: kbenirsc@ucsd.edu
>Please visit my Website on Comparative Placentation at:
>http://medicine.ucsd.edu/CPA
>
>At Tue, 7 May 2002, Regnifob@aol.com wrote:
>>
>>A not so esoteric question
>>
>>An ultrasound may detect a gender which does not jibe with that on a CVS
thus
>>raising a flag to an error in the CVS. Are requests often made to
>>ultrasonographers to specifically use this as a sort of back up to the CVS
>>result when the chromosme result is identical to the mother's and could
>>indicate unsuspected maternal contamination with no other clues?
>>
>>Dr. Bofinger from Cincinnati
>
>--
>Wolfgang Moroder, MD
>Prenatal Unit
>Bolzano General Hospital Italy
>
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