Objective: To describe late-onset generalized chorea in a patient found to have the JAK2V617F mutation without polycythemia vera.

Background: Polycythemia vera (PV) is well-known to be associated with the rare neurological manifestation of chorea. The JAK2V617F mutation is associated with PV but can also be found in patients with other hematologic abnormalities or even normal blood counts.

Methods: Informed consent was obtained from the patient. An 86-year-old right-handed man presented with 1 month of involuntary movements. He had facial grimacing, tongue chewing, grunting, slurred speech, shoulder shrugging, and leg movements. He was able to suppress the movements, felt no urge to move, no restlessness, and did not have the abnormal movements in sleep. After developing the movements, the patient developed canker sores and tooth pain requiring treatment. The patient also had gait difficulty related to weakness after cervical spinal fusion but his gait worsened after onset of involuntary movements. He did not have exposure to neuroleptics or anti-emetics. He had a 17 lb unintentional weight loss over the past 1 month.

Results: General exam was notable for facial plethora and diffuse ecchymoses. On routine lab testing 3 months prior to developing involuntary movements, the patient was noted to have mild leukocytosis. Initially he had WBC count 11.8 with normal differential, low Hgb 11.4 (chronic) and normal platelets 202. Erythropoietin level was 4 (low) and flow cytometry was normal. Further testing revealed JAK2V617F mutation. 6 months later, the patient had WBC 16.4 with normal differential, normal Hgb 14.4 and normal platelets 209. His elevated WBC count is ascribed to a JAK2 mutation-positive myeloproliferative disorder. Workup for other causes of chorea, including Huntington’s disease, was unrevealing.

Conclusions: We conclude that this patient’s chorea is associated with the JAK2V617F mutation. The patient was prescribed hydroxyurea, tetrabenazine and continued on aspirin. Therapeutic phlebotomy was not attempted because of his history of longstanding anemia. His blood counts normalized and chorea improved. Generalized chorea with isolated leukocytosis and JAK2V617F gene mutation has not been previously described. As suggested by Lew et al., this may be another type of forme fruste of the full manifestation of the myeloproliferative disorder. As in that case, our patient does not meet criteria for PV and flow cytometry was normal. Our case demonstrates the importance of checking a CBC as part of the workup for late-onset chorea.

References: 1. Lew J, Frucht SJ, Kremyanskaya M, Hoffman R, Mascarenhas J. Hemichorea in a patient with JAK2V617F blood cells. Blood 2013;121(7):1239-1240. 2. Coppack SW, Gibberd FB. Chorea with transitional myeloproliferative disease. J Royal Soc Med 1985;78:864-866.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/generalized-chorea-in-a-patient-with-isolated-leukocytosis-and-jak2v617f-mutation-a-case-report/