Case Presentation:

A 68-year-old female with infrequent medical follow-up and a past medical history of chronic back pain presented to the ED with right-sided weakness and slurred speech. On the day of presentation she woke up at 11AM with right hand numbness, followed by the onset of right-sided weakness at 1PM, and slurred speech that began at 3PM.  When she presented to the ED at 5PM she noted resolution of the slurred speech but continued to complain of right hand numbness and right sided weakness. CT scan of the head noted a small right subarachnoid hemorrhage in the parietal and occipital lobes. On admission labs, she was found to have a platelet count of 1119. Hematology was consulted, and the patient received 2g of hydroxyurea and was urgently plasmapheresed with improvement of her platelet count to 484 on day 1.  Brain MRI revealed a left precentral gyrus infarct.   She continued to receive hydroxyurea during her hospital course with stabilization of her platelet count in the 700s.  The patient’s right-sided weakness resolved during the admission and right hand numbness improved with only residual 1st and 2nd finger numbness. The patient had a normal TTE and TEE. She was monitored on telemetry without any arrhythmias noted.  Post hospitalization outpatient follow-up noted a normal JAK2 and BCR ABL. 


This case illustrates the severe vascular occlusive disease that can occur in patients with essential thrombocytosis. Although up to 50% of patients are initially asymptomatic and diagnosed incidentally on routine lab work, many patients’ initial presentation of ET is in the context of an ischemic event.  The 15-year risk of thrombosis in patients with ET is estimated to be 22%. The incidence of thrombosis increases with age > 60, prior history of thrombosis, history of diabetes, hypertension, smoking, and the presence of the JAK2 V617F mutation.  It has also been noted that patients over the age of 60 tend to have more hemorrhagic conversion of their thrombotic events. Our patient’s age is consistent with the increased risk of thrombosis and could also help explain the subarachnoid hemorrhage noted on brain imaging. The risk of thrombosis in patients with untreated ET younger than 60 years of age is low. However this risk increases to about 4% per year after the age of 60. Treatment with hydroxyurea in patients over the age of 60 has been shown to decrease the risk of recurrent thrombosis in ET. The use of aspirin to prevent thrombosis in ET has been controversial. In the past, the use of aspirin has been discouraged due to the risk of gastrointestinal bleeding. However, newer evidence suggests that low dose aspirin decreases the risk of thrombosis in ET with a relatively safe GI profile. 


Essential Thrombocytosis is a subgroup of chronic myeloproliferative disorders characterized by a chronic nonreactive thromboythemic state. It is a diagnosis of exclusion once reactive causes and other myeloproliferative disorders are excluded. Though the risk of thrombosis is low, the risk increases after the age of 60 and in the presence of cardiovascular events. The early recognition and treatment of ET can help prevent further tissue damage during vascular occlusive events in these high-risk groups.