| Prevalence | FXTAS affects approximately 1 in 450-500 males and 1 in 150-300 females who carry the *FMR1* premutation[@tassone2012] |
| Typical Onset | Typically begins in the sixth decade of life (50s-60s) |
| Penetrance | Full penetrance by the eighth decade in males; females typically have milder symptoms due to X-inactivation |
| Sex Distribution | More common and severe in males, reflecting the single X chromosome in males |
| Normal | < 45 CGG repeats |
| Premutation | 55-200 CGG repeats |
| Full Mutation | > 200 CGG repeats (causes Fragile X syndrome) |
| FMR1 (Fragile X Mental Retardation 1) | The causative gene; located on chromosome Xq27.3 |
| Brain Atrophy | Cerebellar atrophy (especially of the cerebellar vermis) and cerebral white matter changes |
| Intranuclear Inclusions | Ubiquitin-positive, FMRpolyG-containing inclusions in neurons and astrocytes throughout the brain[@hagerman2020] |
| Loss of Purkinje Cells | Degeneration of cerebellar Purkinje cells contributes to ataxia |
| White Matter Hyperintensities | MRI shows T2/FLAIR hyperintensities in the middle cerebellar peduncles (MCP signs) and periventricular white matter |
| Databases | OMIMOrphanetClinicalTrialsPubMed |