Monozygotic twins discordant for trisomy 21 or chimeric dizygotic twins?

Abstract

We read with interest the article by Rogers et a1 (Am J Med Genet 11: 143-146, 1982) on monozygotic (MZ) twins discordant for trisomy 21. The twins are presumed to be MZ on the basis of placentation, identical blood groups, HLA haplotypes, and serum proteins.We have studied a similar set of twins [Gilgenkrantz et al, 1981a,b]. They were diarnniotic monochorial and their blood groups were identical. One was a normal child and the other had Down Syndrome (DS). Mixoploidy was found in peripheral blood in both of them. We could have concluded monozygoty twins if they had been of the same sex, but the normal child was a boy and the DS child was a girl. In skin fibroblast culture the chromosome constitution conformed to the phenotype 46,XY in the normal boy and 47,XX, +21 in the DS girl.So, we concluded on dizygoty with blood chimerism due to placental vascular anastomoses. We could prove this because the a-1 antitrypsin phenotypes (a serum enzyme of hepatic origin) were different in our twins.Although HLA typing was performed on cultured skin fibroblasts in the case of Rogers et al, we still wonder if their twins could be DZ twins with predominant blood chimera rather MZ twins discordant for trisomy 21.

Plasma‐deposited tetraglyme surfaces greatly reduce total blood protein adsorption, contact activation, platelet adhesion, platelet procoagulant activity, and in vitro thrombus deposition

“…Cheng et al 2006, Dahoun et al 2008, Gilgenkrantz and Janot 1983, Nieuwint et al 1999, O'Donnell et al 2004, Rogers et al 1982, Sethupathy et al 2007…”

“…MZ twins discordant for aneuploidy have been recognized for several decades; discordant MZ twins have been reported for monosomy X, trisomy 1, trisomy 13, and trisomy 21 [Rogers et al, 1982; Weiss et al, 1982; Gilgenkrantz and Janot, 1983; Uchida et al, 1983; Reiss et al, 1993; Nieuwint et al, 1999; O'Donnell et al, 2004; Rohrer et al, 2004; Cheng et al, 2006; Sethupathy et al, 2007; Dahoun et al, 2008; Gentilin et al, 2008; Taylor et al, 2008]. Moreover, unbalanced chromosomal abnormalities have been described in one member from an MZ twin pair [Marcus‐Soekarman et al, 2004; Bourthoumieu et al, 2005].…”

Identical but not the same: The value of discordant monozygotic twins in genetic research

“…MZ twins discordant for aneuploidy have been recognized for several decades; discordant MZ twins have been reported for monosomy X, trisomy 1, trisomy 13, and trisomy 21 [Rogers et al, 1982;Weiss et al, 1982;Gilgenkrantz and Janot, 1983;Uchida et al, 1983;Reiss et al, 1993;Nieuwint et al, 1999;O'Donnell et al, 2004;Rohrer et al, 2004;Cheng et al, 2006;Sethupathy et al, 2007;Dahoun et al, 2008;Gentilin et al, 2008;Taylor et al, 2008]. Moreover, unbalanced chromosomal abnormalities have been described in one member from an MZ twin pair [Marcus-Soekarman et al, 2004;Bourthoumieu et al, 2005].…”

Behavior genetics and postgenomics

“…Once again, the highly stochastic nature of chromosomal aneuploidy and resulting chromosomal mosaicism ensures that MZ twins will have differences in their neuronal chromosomes and that siblings will depart from a presumed 50% possession of the parental nuclear genome. MZ twins discordant for aneuploidy have been recognized for several decades: Discordant MZ twins have been reported for monosomy X, trisomy 1, trisomy 13, trisomy 21, and uniparental disomy (Gilgenkrantz & Janot 1983; Nieuwint et al 1999; Rogers et al 1982; Uchida et al 1983; Weiss et al 1982).…”