A Case of Fragile‐X Associated Tremor/Ataxia Syndrome Presenting with Hemichorea and Strabismus

Chorea is a hyperkinetic movement disorder characterized by flowing or dance-like movements that are random in nature. Chorea due to a focal lesion in the basal ganglia is contralateral, whereas chorea due to metabolic and autoimmune etiologies can be either symmetric or asymmetric.1 The most common cause of hemichorea is stroke, followed by nonketotic hyperglycemic hemichorea.2 In neurodegenerative disorders, however, such as Huntington's Disease, c9orf72 disease, spinocerebellar ataxias, and dentatorubro-pallidoluysian atrophy, chorea is almost always bilateral and symmetric. Here we describe an unusual case of a man presenting with hemichorea and strabismus who was found to have an FMR1 premutation of 90 repeats, confirming the diagnosis of Fragile X tremor/ataxia syndrome (FXTAS). FXTAS can present with abnormal movements such as tremor, cerebellar ataxia, and parkinsonism,3 but reports of chorea are exceedingly rare. To our knowledge, this is the first reported case of hemichorea in FXTAS. A 73-year-old right-handed man was referred to the neurology clinic for double vision. He also reported several months of progressive imbalance and occasional involuntary right arm and leg movements that began gradually and progressed over 6 months. He denied any brief jerking or twitches of his extremities. He denied a change in sensation or weakness in the right arm and leg, and he reported no abnormal movements on his left side. There was no premonitory urge nor relief after the movements. He noticed that he would lose his balance easily when turning, and he had recently fallen while ascending stairs. Around the same time of the onset of the movements he noticed binocular diplopia. His medical history was otherwise significant for hypertension, dyslipidemia, cervical and lumbar stenosis, and depression. His medications included amlodipine, atorvastatin, and vitamin D. In 2016 he was prescribed divalproex 250 mg daily for a month for depressive symptoms then stopped the medication; otherwise, he was not prescribed any other psychiatric medications. At the time of presentation to our clinic he did not display any neuropsychiatric symptoms. He had no exposure to neuroleptics or dopaminergic medications. He did not drink alcohol in excess and denied recreational drug use. The family history was significant for a younger sister with developmental delay; the patient's remaining brother and sister were unaffected neither were their children. The neurologic exam was significant for right upper and lower extremity chorea, action tremor on finger to nose testing bilaterally, and symmetric bradykinesia with finger tapping. We did not observe any entrainment or suggestibility with the chorea. There was no resting tremor or rigidity. Tandem gait was impaired and there was no freezing of gait. Ocular alignment measured both by cover testing and Maddox rod demonstrated V-pattern exotropia, as well as a right hypertropia that increased in left gaze and decreased in up gaze. There was no subjective change in hypertropia with head tilt. There was no spontaneous or gaze-evoked nystagmus. Saccades, pursuit, and vestibulo-ocular reflex were normal. Cognitive screening using the Montreal Cognitive Assessment was 28/30. The rest of the neurologic exam was unremarkable. Laboratory analysis was unremarkable, vitamin B12 was 430 pg/mL (150–900 pg/mL), HbA1c 5.9% (normal