Prenatal diagnosis of mosaic trisomy 20 in New Zealand

Abstract

This series confirms a much lower incidence of phenotypic abnormalities associated with mosaic trisomy 20 compared to other forms of mosaic aneuploidy. Attempts to predict which of these pregnancies will have poor outcomes have not proven to be reliable. We recommend that, if a detailed anatomy scan is normal, parents be counselled that the risk of abnormality is less than 10%. Further tests should be performed only on the basis of a clinical indication.

Long term follow‐up of developmental delay in a child with prenatally‐diagnosed trisomy 20 mosaicism

“…It is a relatively common finding in amniotic cell cultures with a reported incidence of roughly 1 in 7,000 pregnancies tested [Bui et al, 1984; Hsu and Perlis, 1984; Worton and Stern, 1984]. A few groups [Hsu et al, 1987, 1991; Wallerstein et al, 2000; James et al, 2002] have collected data on pregnancy outcome in an effort to determine the associated risks of prenatally diagnosed trisomy 20 mosaicism. To date, no specific phenotype or syndrome has been associated with this cytogenetic finding, and the overwhelming majority of cases (approximately 90%–93%) appear to result in a normal phenotype [Hsu et al, 1987, 1991; Wallerstein et al, 2000; Warren et al, 2001; James et al, 2002].…”

“…A few groups [Hsu et al, 1987, 1991; Wallerstein et al, 2000; James et al, 2002] have collected data on pregnancy outcome in an effort to determine the associated risks of prenatally diagnosed trisomy 20 mosaicism. To date, no specific phenotype or syndrome has been associated with this cytogenetic finding, and the overwhelming majority of cases (approximately 90%–93%) appear to result in a normal phenotype [Hsu et al, 1987, 1991; Wallerstein et al, 2000; Warren et al, 2001; James et al, 2002]. There has been a suggestion of increased risk for congenital heart defects and renal anomalies [Hsu et al, 1991].…”

Expanding the phenotype of mosaic trisomy 20

“…Despite presenting one of the most common mosaicisms detected in prenatal diagnosis, it continues to present a challenge in genetic counseling. Studies which report outcome of these pregnancies suggest a normal result in 90-93% of cases, [Hsu et al, 1987[Hsu et al, , 1991Wallerstein et al, 2000;Steinberg Warren et al, 2001;James et al, 2002]. However, most of the cases in these studies had short follow-up times and much of the data is based on birth records.…”

Uniparental disomy and the phenotype of mosaic trisomy 20: a new case and review of the literature

“…A variety of features have been reported in children with this abnormality (Hsu et al 1991). Studies of prenatally detected cases suggest that a normal child will be born in approximately 90% of cases (Hsu et al 1991;Wallerstein et al 2000;Steinberg Warren et al 2001;James et al 2002). One prenatally diagnosed case developed "linear and whorled nevoid hypermelanosis," a skin condition similar in appearance to hypomelanosis of Ito, and was developmentally delayed (Hartmann et al 2004).…”

“…Some investigators have postulated that the amount of mosaicism would correlate with the severity of phenotype, but this has subsequently been shown to be false (Chudoba et al 1999;Eggerman et al 2001;Salafsky et al 2001;James et al 2002;Velissariou et al 2002;Venditti et al 2004;Wallerstein et al 2005;Willis et al 2007). Many studies have hypothesized that uniparental disomy (UPD) may play a role in phenotype variability, but this has not been widely studied.…”