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Trisomy 2 mosaicism is a rare chromosome disorder characterized by having an extra copy of chromosome 2 in a proportion, but not all, of a person’s cells. Many cases of trisomy 2 mosaicism result in miscarriage during pregnancy. In infants born with trisomy 2 mosaicism, severity as well as signs and symptoms vary widely. Features of trisomy 2 mosaicism may include intrauterine growth restriction (IUGR), any of various birth defects, distinctive facial features, growth delay, developmental delays, and intellectual disabilities.[2273][14687] However, children with trisomy 2 mosaicism with no significant medical problems have been reported (although long-term follow-up was not available).[14687] The severity and specific symptoms present generally depend on the level of mosaicism (the proportion of cells affected) and the location or type of affected cells in the body. Trisomy 2 mosaicism is not inherited. It is caused by a random error in cell division during early development of the embryo.
When trisomy 2 mosaicism is detected during early pregnancy with chorionic villus sampling (CVS), the affected cells may be confined only to the placenta, and not present in the fetus. Amniocentesis is typically recommended to confirm this, and monitoring is still warranted due to an increased risk for intrauterine growth restriction, low amniotic fluid level (oligohydramnios), or other complications including stillbirth.[2282][11627]
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