Triple X syndrome
| Triple X syndrome | |
|---|---|
| Synonyms | triplo-X syndrome, trisomy X, XXX syndrome, 47 XXX syndrome |
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| Increased distance between the eyes in 9 year old girl with trisomy X | |
| Classification and external resources | |
| Specialty | Medical genetics |
| ICD-10 | Q97.0 |
| DiseasesDB | 13386 |
| MeSH | C535318 |
Triple X syndrome, also known as trisomy X and 47 XXX, is characterized by the presence of an extra X chromosome in each cell of a female. Those affected are often taller than average. Usually there is no other physical differences and normal fertility. Occasionally there are learning difficulties, decreased muscle tone, seizures, or kidney problems.
Triple X is due to a random event. Triple X can result either during the division of the mother's reproductive cells or during division of cells during early development. It is not typically inherited from one generation to the next. A form where only a percentage of the body cells contain XXX can also occur. Diagnosis is by chromosomal analysis.
Treatment may include speech therapy, physical therapy, and counseling. It occurs in about one in every 1,000 female births. It is estimated that 90% of those affected are not diagnosed as they either have no or only few symptoms. It was first identified in 1959.
Because the vast majority of triple X females are never diagnosed, it may be very difficult to make generalizations about the effects of this syndrome. The samples that were studied were small and may be nonrepresentative. Because of the lyonization, inactivation, and formation of Barr bodies in all female cells, only one X chromosome is active at any time. Thus, triple X syndrome most often has only mild effects or has no effects. The symptoms vary from person to person, with some women being more affected than others.
Symptoms may include tall stature, vertical skin folds that may cover the inner corners of the eyes (epicanthal folds), poor muscle tone, and a curve in the 5th finger towards the 4th. There may also be a small head (microcephaly). There are seldom any observable physical anomalies in triple X females, other than being taller than average.
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