Diagnosis and Successful Treatment of Chorea in Fragile X-associated Tremor/Ataxia Syndrome with Memantine
Aimen Vanood1, Amir Mbonde2, Shannon Chiu1, Sotiris Mitropanopoulos3
1Mayo Clinic Arizona, 2Neurology, Mayo Clinic Arizona, 3Mayo Clinic
Objective:
Describe an atypical presentation of Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) with “gray zone” CGG repeat and response to memantine.
Background:
FXTAS is a neurodegenerative disorder caused by greater than 200 CGG repeat expansion of the Fragile X mental retardation 1 (FMR1) gene. However, patients with FMR1 premutation (55-200 CGG repeats) and gray zone (47-54 CGG repeats) can experience atypical symptoms, which can pose significant diagnostic and treatment challenges.
Design/Methods:
Case study.
Results:
An 81-year-old female presented with a 6-month history of slowly progressive cognitive decline and atypical tremor. Her mother had an unknown early onset neurodegenerative movement disorder. Initial exam revealed deficits in attention and calculation and was notable for postural and kinetic hand tremor and fidgety abnormal movements of the trunk and extremities which continued to worsen over two years of follow-up. Movement neurophysiology study confirmed that the abnormal movements were due to chorea. She was treated with as needed Clonazepam without benefit. MRI Brain and cerebrospinal fluid testing was unrevealing. Serum testing for metabolic, inflammatory, and nutritional causes was unrevealing as well. Genetic testing for Huntington’s Disease was negative. Whole genome sequencing was pursued due to persistent symptoms, and revealed the patient to be heterozygous for CGG repeat expansion in the FMR1 gene with 47-50 repeats (gray zone). She was started on scheduled Clonazepam 0.25 mg and Memantine with titration to 10 mg twice daily. She experienced significant clinical improvement in her chorea with each uptitration of memantine. Repeat movement neurophysiology study (done after holding Clonazepam) revealed marked reduction in amplitude, duration, and frequency of chorea. She continues to do well after 6-month follow up time.
Conclusions:
This case suggests that chorea can be seen in gray zone FXTAS, with excellent response to Memantine.
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