Not Found

Find information on medical topics, symptoms, drugs, procedures, news and more, written for the health care professional.

* This is the Professional Version. *

Fragile X–Associated Tremor/Ataxia Syndrome (FXTAS)

By Hector A. Gonzalez-Usigli, MD, Instituto Mexicano del Seguro Social, Guadalajara

Click here for
Patient Education

Fragile X–associated tremor/ataxia syndrome (FXTAS) is a genetic disorder affecting mostly men and causing tremor, ataxia, and dementia. Tremor is a common early symptom that is followed by ataxia, parkinsonism, and eventually dementia. Diagnosis is confirmed by genetic testing. Tremor can often be relieved with primidone, propranolol, and/or antiparkinsonian drugs.

FXTAS affects about 1/3000 men > 50. It results from a premutation (50 to 200 CGG repeats) in the Fragile X mental retardation (FMR1) gene on the X chromosome. Fragile X syndrome, the most common form of intellectual disability in males, develops when the mutation is full (> 200 repeats).

People with the premutation are considered carriers. Daughters (but not sons) of men with the premutation inherit the premutation. These daughters' children (grandchildren of the men with the FXTAS premutation) have a 50% chance of inheriting the premutation, which can expand into a full mutation when passed from mother to child (and thus cause Fragile X syndrome).

FXTAS develops in about 30% of men with the premutation and in < 5% of women with the premutation.

Risk of developing FXTAS increases with age.

Symptoms and Signs

FXTAS symptoms become noticeable in late adulthood. The more CGG repeats, the more severe the symptoms and the earlier the onset.

Tremor, often misdiagnosed as essential tremor, is a common early symptom. Patients develop ataxia (which progressively worsens), then parkinsonism, and eventually dementia.

Pearls & Pitfalls

  • Consider FXTAS in patients diagnosed with essential tremor if they develop ataxia or signs of parkinsonism.

Dementia begins with loss of short-term memory, slowed thought, and difficulty problem solving. Depression, anxiety, impatience, hostility, and mood lability may develop.

Peripheral neuropathy is often present, causing loss of sensation and reflexes in the feet . Dysautonomia (eg, orthostatic hypotension) may occur. In later stages, bladder and bowel control may be lost.

Life expectancy after motor symptoms develop ranges from about 5 to 25 yr.

In women with the premutation, symptoms are usually less severe, possibly because the presence of another X chromosome is protective. These women have an increased risk of early menopause, infertility, and ovarian dysfunction.


  • Genetic testing

If FXTAS is suspected, patients should be asked whether any of their grandchildren have intellectual disability and whether their daughters have had early menopause or infertility. Also, grandparents of patients that have Fragile X syndrome should be asked whether they have symptoms suggesting FXTAS; if so, genetic counseling is recommended for their children and/or grandchildren, except for the patient known to have Fragile X syndrome.

MRI is done; it may identify the characteristic increased signal in the middle cerebellar peduncles.

Diagnosis is confirmed by genetic testing.


  • Primidone, propranolol, and/or antiparkinsonian drugs

The tremor in FXTAS can often be relieved with primidone, propranolol, and/or antiparkinsonian drugs.

Resources In This Article

Drugs Mentioned In This Article

  • Drug Name
    Select Trade

* This is the Professional Version. *