Klinefelter syndrome facts for kids

Klinefelter syndrome, also known as 47, XXY or XXY syndrome, is a genetic disorder. This means it's a condition someone is born with because of a small difference in their DNA or chromosomes. People with Klinefelter syndrome have an extra X chromosome. Usually, males have one X and one Y chromosome (XY). But with Klinefelter syndrome, they have two X chromosomes and one Y chromosome (XXY). This is why they are sometimes called "XXY males."

What are Chromosomes?

Inside every cell in your body, there are tiny structures called chromosomes. They are like instruction manuals that tell your body how to grow and work. Humans usually have 46 chromosomes, arranged in 23 pairs. One pair determines if you are male or female. Females usually have two X chromosomes (XX), and males usually have one X and one Y chromosome (XY). In Klinefelter syndrome, a male has an extra X chromosome, making their pattern XXY.

How it Affects People

Males who have Klinefelter syndrome are almost always infertile. This means they cannot have babies of their own. This is one of the main effects of having the extra X chromosome.

Klinefelter in Animals

Humans are not the only ones who can have Klinefelter syndrome. Other male animals can have it too. For example, mice can have this condition.

Male calico or tortoiseshell cats are a good example of Klinefelter syndrome in animals. These cats have special fur patterns that are usually only seen in female cats. This is because the gene for these fur colors is found on the X chromosome. If a male cat has these colors, it often means they have an extra X chromosome, just like humans with Klinefelter syndrome. These cats are important for scientists to study, helping them learn more about the syndrome.

See also

In Spanish: Síndrome de Klinefelter para niños