To present a case of embolic stroke of undetermined source (ESUS) in a patient with a JAK2 mutation, emphasizing the importance of considering myeloproliferative disorders (MPD) in hypercoagulable stroke workup.

Thrombosis is a significant complication of MPD, contributing to morbidity and mortality significantly. Studies show that thrombotic events can precede MPD diagnosis, even without abnormal blood counts. The JAK2 gene mutation (V617F) is found in patients with unexplained or unusual thrombosis, indicating latent MPD. While splanchnic veins are common sites, ischemic stroke is rare.

A 75-year-old female with a history of hypertension, osteoarthritis, and a recent unprovoked right leg deep vein thrombosis (treated with 3 months of apixaban) presented with acute right arm and leg weakness and dysarthria. Neurological examination revealed an NIH Stroke Scale  score of 4. Initial computed tomography (CT) findings were unremarkable, and CT angiography (CTA) ruled out large vessel occlusion. The patient was not eligible for thrombolytic or endovascular treatment. Magnetic resonance imaging confirmed an intermediate-sized left corona radiata stroke. Transthoracic echocardiography demonstrated normal findings with no PFO, and low-density lipoprotein levels (LDL) was at 115 mg/dL. A comprehensive hypercoagulable workup yielded unremarkable results. CT of the chest, abdomen, and pelvis revealed no evidence of malignancy. Complete blood count analysis indicated normal blood counts. Notably, genetic testing done for DVT work up initially revealed a positive JAK2 V617F mutation and hence patient was started on lifelong apixaban.

This case underscores the significance of recognizing JAK2 mutation associated MPD as a potential etiology for ESUS, even in the absence of abnormal cell counts. Early identification of such cases is crucial in formulating appropriate management strategies and reducing the risk of recurrent thrombotic events. This report contributes to the growing body of evidence highlighting the need for a comprehensive hypercoagulable workup in the ESUS.