Fragile X-Associated Disorders
When scientists first discovered the gene that is responsible for fragile X syndrome (FXS), they called it the FMR1 gene.
In addition to FXS, there are other fragile X-associated disorders that are caused by changes in the same FMR1 gene. The FMR1 gene usually makes a protein the scientists called FMRP. FMRP is needed for brain development. Changes in the gene determine whether someone makes less or none of this protein, depending on how much the gene is changed. Fragile X-associated disorders include:
- Fragile X syndrome
- Fragile X-associated primary ovarian insufficiency
- Fragile X-associated tremor/ataxia syndrome
Fragile X Syndrome (Full Mutation)
Fragile X syndrome (FXS) is one of the most common causes of inherited intellectual disability. People who have FXS do not make the protein FMRP. In these people, the FMR1 gene has been turned off. Fragile X syndrome often results from a full mutation of the FMR1 gene.
Other Fragile X-Associated Disorders (Premutation)
People who have other fragile X-associated disorders (not FXS) have changes in their FMR1 gene but usually make some FMRP. In these people, the FMR1 gene is not turned completely off, but the gene does not function normally. Fragile X-associated disorders can be caused by this type of partial change, called a premutation of the FMR1 gene. People with a premutation of the FMR1 gene do not have FXS but may have another fragile X-associated disorder. Some people with a premutation may have noticeable symptoms, and others may not.
Fragile X-Associated Primary Ovarian Insufficiency (FXPOI)
Fragile X-Associated Primary Ovarian Insufficiency (FXPOI) is a cause of infertility and early menopause among adult women. Women with a condition called primary ovarian insufficiency stop having menstrual cycles and have symptoms of menopause before 40 years of age. Women who have a premutation in their FMR1 gene are at higher risk for primary ovarian insufficiency and are at higher risk for having children who have FXS.
Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS)
Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) is a disorder of the nervous system that can cause tremors and problems with walking, balance (also called ataxia), memory, and mood disorders among older adults. FXTAS can be caused by a premutation in the FMR1 gene.