It is hard to predict exactly how long someone with mosaic trisomy 14 will live. Most often, babies that have many cells with the extra chromosome 14 are very sick and die early in life. However, about 2/3 or 67%, of individuals with mosaic trisomy 14 live into childhood. There have been reports of people with mosaic trisomy 14 living into their late 20s. Individuals with fewer cells containing the extra chromosome 14 tend to have less health issues and tend to live longer. Rarely, individuals who have only a very few number of extra chromosome 14 cells, which may be found on prenatal testing, will have few to no medical issues and live a normal life span. It is hard to predict since it may not be clear exactly which cells in the body contain the extra chromosome 14.
When mosaic trisomy 14 is found before a baby is born, through chorionic villus sampling (CVS) or amniocentesis, it can be very difficult to predict what health problems will occur. If the CVS test identified mosaic trisomy 14, then there is a chance that all the trisomy 14 cells are only in the placenta and not in the baby (confined placenta mosaicism). In this case, an amniocentesis may be suggested to look at the baby’s cells directly. If the cells with extra chromosome 14 are in the baby and the placenta, usually the baby’s health is suggested based up on the percent of cells that have the extra chromosome 14. The baby’s health issues will vary and may be determined by factors such as if the test showed the extra chromosome 14 by chorionic villus sample or amniocentesis or both, if the extra chromosome is from mom or dad, and if there are health problems or birth defects seen on ultrasound. Medical geneticists and genetic counselors can be very helpful in discussing the possible outcomes based on this information.
To find a genetic professional near you who can discuss genetic testing, visit the following two sites: A listing of medical geneticists can be found at the American College of Medical Geneticists website ([link url="” target=”_blank”>www.acmg.net) and genetic counselors can be found on the National Society of Genetic Counselors website: [link url="” target=”_blank”>www.nsgc.org.
