Neuropathic features in fragile X premutation carriers

Area of Science:

• Neurology
• Genetics
• Neuroscience

Background:

• Fragile X-associated tremor/ataxia syndrome (FXTAS) is a progressive neurological disorder affecting fragile X premutation carriers.
• FXTAS presents with central nervous system (CNS) dysfunction, including tremor, ataxia, Parkinsonism, and cognitive decline.
• Neuropathic signs have been observed in individuals with FXTAS.

Purpose of the Study:

• To compare neuropathic signs between fragile X premutation carriers and control groups.
• To investigate the relationship between neuropathic signs, CGG repeat length, and motor symptoms (tremor/ataxia).

Main Methods:

• Utilized a neuropathy scale to assess distal tendon reflexes and vibration sense.
• Compared a large cohort of fragile X premutation carriers and controls.
• Subjects underwent neurological examinations and structured videotaping for movement disorder rating.

Main Results:

• Male carriers showed significantly more impairment in total neuropathy, vibration, and reflex scores compared to male controls.
• Female carriers did not exhibit significant differences in neuropathic signs compared to female controls.
• In male carriers, CGG repeat length correlated with total neuropathy and reflex impairments, independent of age.
• Neuropathy scores were associated with ataxia severity but not tremor severity in both male and female carriers.

Conclusions:

• Neuropathic signs are associated with the fragile X premutation.
• These neuropathic signs likely arise from the same mechanism implicated in CNS disease: toxicity from expanded CGG-repeat FMR1 mRNA.
• The findings highlight the peripheral nervous system involvement in FXTAS, particularly in male carriers.