Fragile X-associated Disorders

Fragile X-associated Disorders (FXD) is a family of genetic conditions that can affect individuals in a variety of ways. The conditions are all caused by changes in the gene known as FMR1.

The Three Fragile X-associated Disorders

Fragile X Syndrome

Fragile X syndrome (FXS) is the most common cause of inherited intellectual disability and the most common known genetic cause of autism or autism spectrum disorders. Symptoms of FXS include a range from learning disabilities to more severe cognitive or intellectual disabilities that were previously referred to as “mental retardation.” Delays in speech and language development are common, as are a variety of physical and behavioral characteristics. FXS is caused by a “full mutation” of the FMR1 Gene.

Fragile X-associated Tremor/Ataxia Syndrome

Fragile X-associated tremor/ataxia Syndrome (FXTAS) is a condition that causes balance, tremor and memory problems in some older male (and less commonly, female) “carriers” of the FMR1 gene. FXTAS is caused by a “premutation” of the FMR1 Gene.

Fragile X-associated Primary Ovarian Insufficiency

Fragile X-associated primary ovarian insufficiency (FXPOI) is characterized by decreased ovarian function, which can lead to infertility and early menopause in some female “carriers” of the FMR1 gene. FXPOI is caused by a premutation of the FMR1 Gene.

Fragile X-associated Disorders (FXD) can be passed on by carriers of the FMR1 gene mutation who have no apparent signs of an FXD. In some families a number of individuals may be affected, while in other families a diagnosed individual may be the only known family member to exhibit symptoms. Also, in some families, only carriers are identified and there are no apparently affected family members.