Expanding the phenotype of fragile X-associated tremor/ataxia syndrome: a new female case

A Chinese case of fragile X-associated tremor/ataxia syndrome (FXTAS) with orthostatic tremor:case report and literature review on tremor in FXTAS

BACKGROUND

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late onset, X-linked genetic, neurodegenerative disorder caused by a "premutation (PM)" in the fragile X mental retardation 1 (FMR1) gene. Here we report a case of FXTAS from mainland of China who presented with rare orthostatic tremor. A review of tremor of FXTAS in the literature is also included.

CASE PRESENTATION

A 67-year-old right-handed farmer started with tremor of both legs 8 years ago which was present while standing but absent when sitting or lying and progressed with unsteady gait one and a half years ago. The brain MRI showed high intensity signal in the bilateral middle cerebellar peduncles (MCP) in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images and gene test for premutation for FMR1 was positive with 101 CGG repeats. The patient met the the diagnosis of definite FXTAS. Clonazepam and topiramate were administered to control tremor. We reviewed the literature and identified 64 cases with detailed clinical and genetic information. Orthostatic tremor associated with FXTAS is very rare. We found 85.2% patients reported tremor,42.6% with intention tremor,36.1% with kinetic tremor,32.8% with rest tremor and 29.5% with posture tremor. 37.7% of patients who have tremor showed at least two types of tremor. There were 6 patients with isolated rest tremor. There was 2 patient with voice tremor and 6 with head tremor. We also found that 74.6% FXTAS patients had family history of FMR1 gene associated diseases including Fragile X syndrome (FXS), FXTAS or fragile X-associated primary ovarian insufficiency (FXPOI).

CONCLUSIONS

Adding our data to the available literature suggests that orthostatic tremor could be a rare initial manifestation of FXTAS and the review will increasing our understanding the phenotype of tremor in FXTAS. Family history of FMR1 gene associated diseases might be an important clue to the diagnosis.

Understanding the neuropsychiatric phenotype of fragile X-associated tremor ataxia syndrome: a systematic review

Fragile X-associated tremor ataxia syndrome (FXTAS) is a recently identified X-linked neurodegenerative disorder affecting a proportion of premutation carriers of the Fragile X Mental Retardation 1 (FMR1) gene. Previous research suggests that cognitive and psychiatric features of FXTAS may include primary impairments in executive function and increased vulnerability to mood and anxiety disorders. A number of these reports, however, are based on overlapping cohorts or have produced inconsistent findings. A systematic review was therefore conducted to further elucidate the neuropsychiatric features characteristic of FXTAS. Fourteen papers met inclusion criteria for the review and were considered to represent nine independent FXTAS cohorts. Findings from the review suggest that the neuropsychiatric phenotype of FXTAS is characterised primarily by poorer performance on measures of executive function, working memory, information processing speed, and fine motor control when compared to matched comparison groups. Two studies were identified in which psychiatric symptoms in FXTAS were compared with controls, and these yielded mixed results. Overall the results of this review support previous reports that the neuropsychiatric profile of FXTAS is consistent with a dysexecutive fronto-subcortical syndrome. However, additional controlled studies are required to progress our understanding of FXTAS and how the neuropsychiatric profile relates to underlying pathological mechanisms.

Clinical neurogenetics: fragile x-associated tremor/ataxia syndrome

This article summarizes the clinical findings, genetics, pathophysiology, and treatment of fragile X-associated tremor ataxia syndrome. The disorder occurs from a CGG repeat (55-200) expansion in the fragile X mental retardation 1 gene. It manifests clinically in kinetic tremor, gait ataxia, and executive dysfunction, usually in older men who carry the genetic abnormality. The disorder has distinct radiographic and pathologic findings. Symptomatic treatment is beneficial in some patients. The inheritance is X-linked and family members may be at risk for other fragile X-associated disorders. This information is useful to neurologists, general practitioners, and geneticists.

Fragile x-associated tremor ataxia syndrome: the expanding clinical picture, pathophysiology, epidemiology, and update on treatment

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a progressive degenerative movement disorder characterized by kinetic tremor, cerebellar gait ataxia, parkinsonism, and cognitive decline. This disorder occurs in both males and females, frequently in families with children who have fragile X syndrome. The clinical features of this disorder, both classic and newly described, are summarized in this paper. In screening studies, fragile X mental retardation 1 (FMR1) gene premutation (55–200 CGG) expansions are most frequently seen in men with ataxia who have tested negative for spinocerebellar ataxias. Since the original description, the classic FXTAS phenotype has now been reported in females and in carriers of smaller (45–54 CGG) and larger (>200 CGG) expansions in FMR1. Premutation carriers may present with a Parkinson disease phenotype or hypotension, rather than with tremor and/or ataxia. Parkinsonism and gait ataxia may also be seen in individuals with gray zone (41–54 CGG) expansions. Studies regarding medication to treat the symptoms in FXTAS are few in number and suggest that medications targeted to specific symptoms, such as kinetic tremor or gait ataxia, may be most beneficial. Great progress has been made in regards to FXTAS research, likely given the readily available gene test and the screening of multiple family members, including parents and grandparents, of fragile X syndrome children. Expansion of genotypes and phenotypes in the disorder may suggest that a broader disease definition might be necessary in the future.

Fragile X-associated tremor/ataxia syndrome: clinical phenotype, diagnosis, and treatment

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by a CGG repeat expansion in the premutation range (55-200) in the fragile X mental retardation 1 gene. Onset is typically in the early seventh decade, and men are principally affected. The major signs are cerebellar gait ataxia, intention tremor, frontal executive dysfunction, and global brain atrophy. Other frequent findings are parkinsonism (mild), peripheral neuropathy, psychiatric symptoms (depression, anxiety, and agitation), and autonomic dysfunction. The clinical presentation is heterogeneous, with individuals presenting with varied dominating signs, such as tremor, dementia, or neuropathy. Magnetic resonance imaging shows atrophy and patchy white matter lesions in the cerebral hemispheres and middle cerebellar peduncles. The latter has been designated the middle cerebellar peduncle sign, which occurs in about 60% of affected men, and is relatively specific for FXTAS. Affected females generally have less severe disease, less cognitive decline, and some symptoms different from that of men, for example, muscle pain. Management of FXTAS is complex and includes assessment of the patient's neurological and medical deficits, treatment of symptoms, and provision of relevant referrals, especially genetic counseling. Treatment is empirical, based on anecdotal experience and on knowledge of what works for symptoms of other disorders that also exist in FXTAS. Presently, the disorder is underrecognized because the first published report was only in 2001 and because the presentation is variable and mainly consists of a combination of signs common in the elderly. However, accurate diagnosis is critical for the patient and for the family because they need education regarding their genetic and health risks.

Dementia in Fragile X-associated Tremor/Ataxia Syndrome

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a cause of movement disorders and cognitive decline which has probably been underdiagnosed, especially if its prevalence proves similar to those of progressive supranuclear palsy and amyotrophic lateral sclerosis. We report a case of a 74-year-old man who presented with action tremor, gait ataxia and forgetfulness. There was a family history of tremor and dementia, and one of the patient’s grandsons was mentally deficient. Neuropsychological evaluation disclosed a frontal network syndrome. MRI showed hyperintensity of both middle cerebellar peduncles, a major diagnostic hallmark of FXTAS. Genetic testing revealed premutation of the FMR1 gene with an expanded (CGG)₉₀ repeat. The diagnosis of FXTAS is important for genetic counseling because the daughters of the affected individuals are at high risk of having offspring with fragile X syndrome. Tremors and cognitive decline should raise the diagnostic hypothesis of FXTAS, which MRI may subsequently reinforce, while the detection of the FMR1 premutation can confirm the condition.