The distribution of chromosomal genotypes associated with Turner's syndrome: livebirth prevalence rates and evidence for diminished fetal mortality and severity in genotypes associated with structural X abnormalities or mosaicism

Abstract

The proportions of chromosomal genotypes associated with the Turner syndrome genotype (excluding those with a Y chromosome) in embryonic and fetal deaths, in fetuses diagnosed prenatally, and in living individuals were reviewed. The ratio of apparent non-mosaic 45,X to 45,X/46,XX mosaics was notably higher in a New York City series of embryonic and fetal deaths, 13.5 to 1, than in living individuals reported to the New York State Chromosome Registry, 3.6 to 1. The ratios of 45,X cases to those with 46,Xi(Xq) was 5.7 to 1 in living individuals, but was 112 to 0 in embryonic and fetal deaths, an even greater disparity, indicating the marked fetoprotective effect of more than one dose of some locus or loci on the long arm of the X chromosome. The results of review of data pertinent to the livebirth prevalence of the (apparent non-mosaic) 45,X genotype suggest a rate of about 5.7 per 100,000 livebirths (11.8 per 100,000 females) with 95% confidence limits of 2.6 per 100,000 to 10.8 per 100,000. The rate in fetuses diagnosed prenatally is 8/27,202, about 30 per 100,000. As a large proportion of these, perhaps 75%, would undergo spontaneous fetal death if not terminated electively, these figures are consistent with the direct estimate of livebirth rates. The rate of all those with X chromosome abnormalities (with a Y chromosome) associated with signs or symptoms that eventually lead to referral for cytogenetic study was estimated at a minimum of 10.7 per 100,000 livebirths, (22.2 per 100,000 females).

Frequency of 677C -> T and 1298A -> C polymorphisms in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene in Turner syndrome individuals

“…Turner syndrome individuals frequently show mosaicism (Hook and Warbuton, 1983;Robinson, 1990) and the presence of a normal cell lineage along with the 45,X lineage is considered to increase the probability of survival of those with 45,X Turner syndrome (Held et al, 1992, Kelly et al, 1992.…”

Disgenesias gonadais e tumores: aspectos genéticos e clínicos

“…A incidência da ST é estimada em torno de 0,47 por 1.000 ou 1 em cada 2.130 nativivas (38). O número de recém-nascidas corresponde, porém, a uma pequena fração do total de conceptos com ST, uma vez que, embora 1 a 2% de todas as concepções humanas tenha a constituição cromossômica 45,X, cerca de 99% dos conceptos 45,X são abortados espontaneamente (39).…”

Analysis of the SRY Gene in Turner Syndrome Patients from the Republic of Macedonia

“…Approximately half of the unidentifiable marker chromosomes that have an estimated frequency of 3% are Y-derived [6,7]. It has been speculated that most Turner syndrome patients with putative non mosaic 45,X karyotype have an undetected mosaicism, based on an analysis which revealed that less than 1% of 45,X conceptions survive pregnancy [8]. Several investigators have postulated that in 45,X patients, fetal survival needs SRY GENE IN TURNER SYNDROME mosaicism in at least some organ or tissue [8,9].…”

“…It has been speculated that most Turner syndrome patients with putative non mosaic 45,X karyotype have an undetected mosaicism, based on an analysis which revealed that less than 1% of 45,X conceptions survive pregnancy [8]. Several investigators have postulated that in 45,X patients, fetal survival needs SRY GENE IN TURNER SYNDROME mosaicism in at least some organ or tissue [8,9]. Patients with the SRY gene require special attention since the presence of a Y chromosome correlates with a 10-20% risk of developing gonadoblastoma or dys germinoma later in life [10,11].…”

“…SRY GENE IN TURNER SYNDROME mosaicism in at least some organ or tissue [8,9]. Patients with the SRY gene require special attention since the presence of a Y chromosome correlates with a 10-20% risk of developing gonadoblastoma or dys germinoma later in life [10,11].…”