About Fragile X

What is Fragile X?

Fragile X occurs when there is a change, called a mutation, in a single gene called the FMR1 gene. Every human being has this gene. Some people have only a small change in this gene (referred to as a premutation) and may not show any symptoms associated with Fragile X. Persons with the premutation are called carriers and are at risk to develop other related conditions (see FXTAS and FXPOI below). Other people may have bigger changes in the gene (called a full mutation), which can cause the symptoms of Fragile X Syndrome.

Fragile X is inherited, which means it is passed down from parent to child. The changes in the gene can become greater when passed from mother to child, so a woman who has no symptoms related to Fragile X can have a child affected with Fragile X Syndrome. A male carrier can only pass the premutation, and will pass it to all of his daughters, but none of his sons. Fragile X affects people of all ethnicities, races, and socio-economic backgrounds. Fragile X is named because of the appearance of the X chromosome where the gene mutation occurs, not because individuals with the FMR1 mutation are in any way “fragile”. Read More