Last Reviewed June 2, 2009
Symptoms & Characteristics
Triploidy is a chromosomal condition characterized by an entire extra set of chromosomes in each cell of a person's body. Therefore, affected people have 69 chromosomes, instead of the typical 46. Both males and females can be affected with this condition.
The majority of pregnancies affected with Triploidy will spontaneously miscarry during the pregnancy. For those few pregnancies that do survive until birth, there can be placental problems, severe growth restriction and multiple birth defects. Many affected fetuses are stillborn. The physical birth defects seen in fetuses affected with triploidy are variable. The exact pattern of anomalies depends upon whether the extra set of chromosomes was inherited from the mother or from the father.
Treatment
There is no cure or treatment for Triploidy. This condition is lethal.
How Common Is It?
About 1% to 3% of recognized pregnancies worldwide are affected with triploidy. However, only about 1 in 50,000 newborns are affected with triploidy, as the majority of affected pregnancies will spontaneously miscarry.
Genetics & Inheritance
All of our genes are packaged together on chromosomes. People typically have 46
chromosomes in total, which are grouped into 23 pairs. The first 22 pairs
are numbered largest to smallest (1-22) and are called autosomes. The
last pair are called the sex chromosomes and determine gender, either XX
(female) or XY (male). We typically inherit 23 chromosomes (one of each pair)
from our mother (in an egg cell) and the other 23 from father (in a sperm
cell).
Triploidy typically occurs sporadically. Triploidy is caused by the presence of an entire extra set of chromosomes, for a total of 69 chromosomes in the affected person. Therefore, fetuses affected with triploidy can be 69,XXX (female), or 69,XXY (male), or 69,XYY (male). Triploidy can occur in more than one way. The most common cause of triploidy is the fertilization of a single egg by two sperm. The other cause of triploidy is when all of the chromosomes in either the developing egg or sperm fail to separate during cell division. The result is an egg/sperm cell with an extra set of all chromosomes. When this egg/sperm with 46 chromosomes (instead of 23) is fertilized by a sperm/egg with 23 chromosomes, the resulting fetus now has 69 chromosomes.
There are other genetic conditions that have symptoms that overlap with Triploidy. A genetic consultation with a trained genetic professional is important for a complete evaluation, accurate diagnosis, as well as discussion of the benefits and limitations of chromosome testing and recurrence risk.
Genetic Testing
Triploidy can be diagnosed by a
chromosome analysis, which is available through an
in person
genetic consultation for people who are considered at risk. Use
our
find a genetic professional directory to locate a trained genetic professional in your area.
Support & More Information
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Alternative Names
- Triploid syndrome
- Chromosome Triploidy Syndrome
- Triploidy Syndrome
- 3n Syndrome
- Diploid/Triploid Mixoploidy
- 2n/3n Mixoploidy