[4][5] The main clinical features of FXTAS include problems of movement with cerebellar gait ataxia and action tremor.

[7] In contrast to FXS full mutation, which is diagnosed early in childhood, symptoms of FXTAS manifest in individuals over the age of 50.

[2][3] FMR1 mRNA is found to be elevated in patients with FXTAS[7] in contrast to FXS, where the FMR1 gene is transcriptionally silenced via DNA methylation.

This includes increased irritability, angry outbursts, and impulsive behaviour[citation needed] FXTAS can be diagnosed using a combination of molecular, clinical, and radiological findings.

A definite, probable, or possible diagnosis of FXTAS can be assigned based on combined clinical or radiological findings in conjunction with the molecular premutation.

Minor symptoms such as parkinsonism, short-term memory deficit, and executive function decline can further contribute to a diagnosis of FXTAS.

Current treatment includes medications for alleviating symptoms of tremor, ataxia, mood changes, anxiety, cognitive decline, dementia, neuropathic pain, or fibromyalgia.

[citation needed] FXTAS has shown strong age-dependent penetrance, affecting older premutation carriers with greater prevalence.

However, due to X-inactivation, female carriers are much less likely to develop dementia or classic ataxia and tremor, instead demonstrating symptoms such as fibromyalgia, thyroid disease, hypertension, and seizures.