Fragile X-associated tremor/ataxia syndrome

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a genetic disorder characterized by progressive cerebellar ataxia and tremor. It is associated with the FMR1 gene, which is also linked to Fragile X syndrome, the most common form of inherited intellectual disability. FXTAS typically affects older adults, with symptoms often beginning in the 50s or 60s. The condition is more common in males than in females.

Symptoms

The primary symptoms of FXTAS include intention tremor, which is a shaking that occurs during voluntary movements, and ataxia, or lack of coordination. These symptoms can lead to difficulties with walking, writing, and other tasks that require fine motor skills. Other symptoms may include memory problems, cognitive decline, anxiety, and mood swings. In advanced stages, individuals may experience significant neurological problems, including severe tremor and problems with movement and balance.

Causes

FXTAS is caused by a mutation in the FMR1 gene. Unlike Fragile X syndrome, which is caused by a full mutation (over 200 CGG repeats) in the FMR1 gene, FXTAS is associated with a premutation, where the gene has 55 to 200 CGG repeats. This premutation can increase the level of FMR1 mRNA, leading to toxicity and cellular damage over time. The exact mechanism by which the premutation causes the symptoms of FXTAS is still under investigation.

Diagnosis

Diagnosis of FXTAS involves a combination of clinical evaluation and genetic testing. Neurological examination can reveal signs of tremor and ataxia, while a detailed family history can provide clues about the genetic basis of the condition. Genetic testing is used to identify the FMR1 premutation. Brain imaging, such as MRI, may show characteristic changes associated with FXTAS, including white matter lesions in the cerebellum and brainstem.

Treatment

There is currently no cure for FXTAS, and treatment focuses on managing symptoms and improving quality of life. Medications may be prescribed to reduce tremor and improve balance. Physical therapy can help maintain mobility and prevent falls. In some cases, speech therapy may be recommended to address communication difficulties. Cognitive behavioral therapy (CBT) and other forms of counseling can help manage mood symptoms and cognitive decline.

Prognosis

The progression of FXTAS can vary widely among individuals. Some may experience a slow progression of symptoms, while others may see a more rapid decline in function. Early intervention and management of symptoms can help improve quality of life, but the condition is ultimately degenerative and can lead to significant disability.

Epidemiology

FXTAS is considered a rare disorder, but its exact prevalence is unknown. It is estimated that 1 in 3,000 to 4,000 males and a smaller proportion of females carry the FMR1 premutation and are at risk for developing FXTAS.

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