Objective:

Examine the connection between essential thrombocythemia (ET) and late-onset movement disorders. 

Background:

An 86-year-old woman with a history of hypertension presented with several weeks of involuntary head and mouth movements. More recently, the movements extended to her extremities, involving the right side more than left. These movements were continuous, choreoathetoid and significantly impaired the patient’s ability to care for herself. She had no history of dopamine-blocking medication use and no family history of movement disorders. Serum studies, including ceruloplasmin, ANA, anti-TTG, and anti-TPO antibodies were within normal limits. Lumbar puncture (including paraneoplastic panel) and EEG were unremarkable. MRI brain revealed scattered embolic infarcts with right MCA territory predominance, although there were no strokes in the basal ganglia or other locations that might explain her involuntary movements. This prompted further imaging, which identified an infarct of the left kidney. Despite extensive stroke workup, her diagnosis remained “embolic strokes of undetermined source.”
The patient’s only persistent lab abnormalities were thrombocytosis and mild leukocytosis without evidence of systemic infection. Given known association between polycythemia vera and chorea, there was suspicion that the thrombocytosis was responsible for both her movement disorder and multifocal infarcts.  

Design/Methods:

Case study.

Results:

Hematologic workup revealed JAK2+ mutation. In the context of persistent thrombocytosis, she was diagnosed with ET and started on hydroxyurea at the recommendation of the hematology service. The patient had some improvement of her involuntary movements after starting tetrabenazine. 

Conclusions:

This dramatic presentation of late-onset chorea seems likely an effect of newly-diagnosed ET. This rare cause of chorea has only four other cases identified in the literature. This particular case is of interest as chorea was the patient’s only presenting symptom – although she also sustained infarcts to the brain and kidney, these events were clinically silent. The identification and treatment of her hematologic disorder may have prevented future complications.