Triple X syndrome

What is triple X syndrome?

Triple X syndrome, also called trisomy X or 47,XXX, is characterized by the presence of one extra X chromosome in each of a female's cells. Most often, this chromosomal change causes no unusual physical features or medical problems. Females with triple X syndrome are sometimes taller than average and have an increased risk of learning disabilities and delayed speech and language skills. Developmental delays and behavioral problems are also possible, but these characteristics vary widely among affected girls and women. Most females with triple X syndrome have normal sexual development and are able to conceive children.

How common is triple X syndrome?

This condition occurs in about 1 in 1,000 newborn girls. Five to 10 girls with triple X syndrome are born in the United States each day.

What are the genetic changes related to triple X syndrome?

Triple X syndrome is related to the X chromosome.

People normally have 46 chromosomes in each cell. Two of the 46 chromosomes are sex chromosomes, called X and Y. Females have two X chromosomes (46,XX), and males have one X chromosome and one Y chromosome (46,XY).

Triple X syndrome results from an extra copy of the X chromosome in each of a female's cells. As a result of the extra X chromosome, each cell has a total of 47 chromosomes (47,XXX) instead of 46. It remains uncertain why an extra copy of the X chromosome is associated with tall stature and learning problems in some girls and women.

Some females with triple X syndrome have an extra X chromosome in only some of their cells. These cases are called 46,XX/47,XXX mosaics.

Can triple X syndrome be inherited?

Trisomy X usually is not inherited, but occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of the X chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a female child, the child will have an extra X chromosome in each of the body's cells.

In some cases, trisomy X results from nondisjunction during cell division in early embryonic development. These cases are usually 46,XX/47,XXX mosaics.

Triple X Syndrome on Wikipedia

'''Triple X syndrome''' is a chromosome aneuploid abnormality characterized by the presence of an extra X chromosome in each cell (biology) of a human female. The syndrome is also known as '''XXX syndrome''', '''trisomy X''', '''triplo-X''', '''47xxx''', or '''47,XXX aneuploidy'''. Trisomy-x results during division of a parent's reproductive cells. Females with Trisomy-x are typically tall with slightly higher sensitivity levels, and are not at any increased risk for medical problems.

Symptoms

Due to the lyonization, inactivation and formation of a Barr body in all female cells, only one X chromosome is active at any time in a female cell. Thus, triple X syndrome most often causes no unusual physical features or medicine problems. Females with the syndrome are usually human height than average, may have menstrual cycle irregularities, and, although rarely exhibiting severe Mental retardation, sometimes have an increased risk of learning disability and delayed speech and language skills. Researchers are not yet certain why an extra copy of the X chromosome is associated with tall stature and learning issues in some girls and women. These characteristics vary widely among affected individuals, however. Additionally, most females with triple X syndrome have normal human sexuality and are able to fertilisation children.

Cause

Triple X syndrome is not inherited, but usually occurs as a random event during the formation of reproductions (ovum and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an oocyte or sperm cell may gain an extra copy of the X chromosome as a result of the nondisjunction. If one of these atypical reproductive cells contributes ... [ Read More ]

External Resources

High Altitude Pathology Institute - High altitude travel advice. Information on chronic mountain sickness, high altitude pulmonary edema, the use of hyperoxic/hypoxic adaptation chambers, and triple hypoxia syndrome.

Triple X Syndrome - Information and support for parents with daughters having this gennetic disorder, with scientific literature and contacts.

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