Merck Manual

Please confirm that you are a health care professional

honeypot link

Fragile X–Associated Tremor/Ataxia Syndrome (FXTAS)


Alex Rajput

, MD, University of Saskatchewan;

Eric Noyes

, MD, University of Saskatchewan

Reviewed/Revised Feb 2024

Fragile X–associated tremor/ataxia syndrome 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 medications.

Fragile X–associated tremor/ataxia syndrome (FXTAS) results from a premutation (50 to 200 CGG repeats) in the Fragile X mental retardation (FMR1) gene on the X chromosome. Fragile X syndrome Fragile X Syndrome Fragile X syndrome is a genetic abnormality on the X chromosome that leads to intellectual disability and behavioral disorders. Diagnosis is with molecular DNA analysis. Treatment is supportive... read more , 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).

Risk of developing FXTAS increases with age and the number or CGG repeats.

Symptoms and Signs of FXTAS

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

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.

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

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.

Diagnosis of FXTAS

  • 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, if a patient has Fragile X syndrome, clinicians should determine whether the patient's grandparents have symptoms suggesting FXTAS; if so, genetic counseling is recommended for the grandparent's children and grandchildren.

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

Diagnosis of FXTAS is confirmed by genetic testing.

Treatment of FXTAS

Treatment references

Key Points

  • Fragile X–associated tremor/ataxia syndrome (FXTAS) affects about 1/3000 men > 50; Fragile X syndrome, the most common cause of intellectual disability in males, develops when the gene mutation is full (more repeats).

  • Ask patients whether any of their grandchildren have intellectual disability and whether their daughters have had early menopause or infertility, and ask grandparents of patients with Fragile X syndrome whether they have symptoms suggesting FXTAS.

  • Do genetic testing to confirm the diagnosis.

  • Treat tremor with primidone, propranolol, topiramate, gabapentin, pregabalin, benzodiazepines, and/or antiparkinsonian medications.

Drugs Mentioned In This Article

Drug Name Select Trade
HEMANGEOL, Inderal, Inderal LA, Inderal XL, InnoPran XL
EPRONTIA, Qudexy XR, Topamax, Topamax Sprinkle, Topiragen , Trokendi XR
Active-PAC with Gabapentin, Gabarone , Gralise, Horizant, Neurontin
Lyrica, Lyrica CR
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!