47,XYY Syndrome
What is 47,XYY syndrome?
47,XYY syndrome is characterised by an extra copy of the Y chromosome in each of a male's cells. Most often, this chromosomal change causes no unusual physical features or medical problems. Males with 47,XYY syndrome are sometimes taller than average and have an increased risk of learning disabilities and delayed speech and language skills. Developmental delays and behavioural problems are also possible, but these characteristics vary widely among affected boys and men. Most males with 47,XYY syndrome have normal sexual development and are able to conceive children.
How common is 47,XYY syndrome?
About 1 in 1,000 males is born with an extra copy of the Y chromosome in each cell. Five to 10 boys with 47,XYY syndrome are born in the United States each day.
What are the genetic changes related to 47,XYY syndrome?
47,XYY syndrome is a chromosomal condition related to the Y 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).
47,XYY syndrome is caused by the presence of an extra copy of the Y chromosome in each of a male's cells. As a result of the extra Y chromosome, each cell has a total of 47 chromosomes instead of 46. It remains uncertain why an extra copy of the Y chromosome is associated with tall stature and learning problems in some boys and men.
Some males with 47,XYY syndrome have an extra Y chromosome in only some of their cells. These cases are called 46,XY/47,XYY mosaics.
Can 47,XYY syndrome be inherited?
47,XYY syndrome usually is not inherited, but occurs as a random event during the formation of sperm cells. An error in cell division called nondisjunction can result in sperm cells with an extra copy of the Y chromosome. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra Y chromosome in each of the body's cells.
In some cases, the addition of an extra Y chromosome results from nondisjunction during cell division in early embryonic development. These cases are usually 46,XY/47,XYY mosaics.
What other names do people use for 47,XYY syndrome?
- XYY Karyotype
- XYY syndrome
- YY syndrome
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