Triple X Syndrome

What is Triple X Syndrome?
Triple X syndrome is a genetic condition found only in females that is caused by a chromosome variation that occurs before a baby is conceived.^1,2 The scientific term for the error that occurs prior to conception and causes Triple X syndrome is "nondisjunction." ¹ The term means that the chromosomes in either the egg or the sperm involved in conception did not separate properly so that the baby ends up with an extra X chromosome. People without Triple X syndrome have a total of 46 chromosomes and those with Triple X syndrome have 47 chromosomes. ¹ People with Triple X syndrome are all females because they do not have a Y chromosome. ² Women with Triple X syndrome have three X chromosomes instead of the usual two ( karyotypes). The chromosomes of women with Triple X syndrome are described as 47, XXX. ³ The 47 indicates that 47 chromosomes are present and the XXX means that the woman has three X chromosomes.³

Triple X syndrome is a relatively common condition affecting about 1 in every 1200 females.³ Unlike other conditions occurring when a person is born with an extra chromosome (such as Trisomy 13,18, or 21 ), people with one extra X chromosome typically do not have any physical birth defects or mental retardation.³

Females with Triple X syndrome may experience learning disabilities and social interaction difficulties.³ Females with Triple X syndrome are usually not infertile. ³ Most females with Triple X syndrome are never diagnosed due to the lack of physical birth defects and medical problems associated with the condition. ¹

References

1. Nussbaum RL, McInnes RR, Willard HF. Thompson & Thompson Genetics in Medicine. 6th ed. Philadelphia, Pa: W.B. Sounders Company, 2001.
2. Therman E, Susman M. Human Chromosomes: Structure, Behavior, and Effects. 3rd ed. New York, NY; Springer-Verlag; 1993.
3. Robinson A, Linden M. Clinical Genetics Handbook. 2nd ed. Ann Arbor, Mi: Blackewll Scientific Publications Inc; 1993:11:109-111.

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