Monozygotic twins with 45,X/46,XY mosaicism discordant for phenotypic sex

Abstract

We report on two sets of monozygotic twins (MZTs) discordant for phenotypic sex ascertained at birth when the female twin was noted to have signs of the Ullrich-Turner syndrome. Cytogenetic investigations on the female of the first pair showed 45,X/46,XY mosaicism in lymphocytes but fibroblasts grown from two skin biopsies at separate sites and from gonadal tissue showed only 45,X cells. The male showed mosaicism in both blood lymphocytes and skin fibroblasts. In the second family, both twins also showed mosaicism in lymphocytes. The female had a 45,X karyotype in fibroblasts from skin and gonadal tissue, but in contrast to the first family, the male twin had a normal male karyotype in fibroblasts from skin biopsy and from connective tissue adjacent to the vas deferens. Discordant phenotypic sex in monozygotic twins is rare. As in our cases, the nine previously reported sets of MZTs all had mosaicism for sex chromosome abnormalities. A mitotic error leading to the loss of a Y chromosome prior to, accompanying, or following the twinning process would account for the reported combinations of karyotypes.

Genetic or epigenetic difference causing discordance between monozygotic twins as a clue to molecular basis of mental disorders

“…These include Turner syndrome, 22 skin pigmentation, 23 minor anomalies, 24 and sex phenotypes. 25,26 Since there are a number of case reports of MZ discordant twins caused by mosaicism of chromosomal abnormality, it may be a frequent cause of discordance in MZ twins. However, it might be biased by methodology.…”

45,X/46,XY mosaicism and Oculo-Auriculo-Vertebral Spectrum following an IVF pregnancy: a report and a discussion of their interrelationships

“…Supporting evidence for an association between MZ twinning and 45,X/46XY mosaicism includes: (1) A number of pairs of MZ twins in which one or both twins had 45,X/46,XY mosaicism have been reported (reviewed in Costa et al 1998) [11]. Notably, in the majority of these cases the females had manifestations of Turner syndrome, and MZ twinning is more frequent in families of patients with Turner syndrome (Boles et al 1987).…”

Prenatal diagnosis of heterokaryotypic mosaic twins discordant for fetal sex

“…However, the conclusions of Hsu are not applicable in every case of twin pregnancies, because an intrauterine exchange of lymphocytes through vessel anastomoses can lead to a falsi®cation of the results. Costa et al (1998) Gonsoulin et al showed in their analysis of 17 persons with a 45,X/ 46,XY cell mosaic that in only ®ve cases did the sets of chromosomes in the lymphocytes match those in the ®broblasts of the skin.…”

“…The phenotype can vary from a normal male child to a classical Ullrich±Turner syndrome (UTS) (Hsu, 1989;Chang et al, 1990). A review of the literature showed that there are only ®ve case reports of monozygotic twins with discrepant sex, of which one or both twins showed a 45,X/46,XY cell mosaic in ®broblasts or gonadal cells (Edwards et al, 1966;Karp et al, 1975;Reindollar et al, 1987;Fujimoto et al, 1991;Costa et al, 1998). In another ten case reports of monozygotic twins with discrepant sex, the karyotype in ®broblasts or gonadal cells was not a 45,X/46,XY mosaic or was not described (Turpin et al, 1961;Schmidt et al, 1976;Dallapiccola et al, 1985;Arizawa et al, 1988;Gonsoulin et al, 1990;Perlman et al, 1990;Kurosawa et al, 1992;Yokota et al, 1994;Pfeiffer 1996;Costa et al, 1998).…”