The fragile X mental retardation 1 gene (FMR1): historical perspective, phenotypes, mechanism, pathology, and epidemiology

Objectives: To provide an historical perspective and overview of the phenotypes, mechanism, pathology, and epidemiology of the fragile X-associated tremor/ataxia syndrome (FXTAS) for neuropsychologists. Methods: Selective review of the literature on FXTAS. Results: FXTAS is an X-linked neurodegenerative disorder of late onset. One of several phenotypes associated with different mutations of the fragile X mental retardation 1 gene (FMR1), FXTAS involves progressive action tremor, gait ataxia, and impaired executive functioning, among other features. It affects carriers of the FMR1 premutation, which may expand when passed from a mother to her children, in which case it is likely to cause fragile X syndrome (FXS), the most common inherited developmental disability. Conclusion: This review briefly summarizes current knowledge of the mechanisms, epidemiology, and mode of transmission of FXTAS and FXS, as well as the neuropsychological, neurologic, neuropsychiatric, neuropathologic, and neuroradiologic phenotypes of FXTAS. Because it was only recently identified, FXTAS is not well known to most practitioners, and it remains largely misdiagnosed, despite the fact that its prevalence may be relatively high.