Prevalence and Clinical Characteristics of Patients with Ischemic Stroke with JAK2V617F Mutation and Normal Blood Counts

ObjectiveThe JAK2 V617F mutation increases the risk of thrombosis in patients with myeloproliferative neoplasms (MPNs). However, it remains unclear whether individuals who carry the JAK2 V617F mutation without MPN also have an increased risk of stroke. MethodsWe prospectively tested for the JAK2 617F mutation in consecutive patients with acute ischemic stroke or transient ischemic attack (TIA) admitted between January 2020 and September 2024. Patients with overt MPN or abnormal blood counts were excluded. We used allele-specific PCR to detect the mutations. ResultsIn total, 921 patients (median age, 77 years; 557 men (62%); TIA, 32 patients) were enrolled in this study. Among them, 11 patients (1.2%; median age, 72 years; 8 male) tested positive for the JAK2 V617F mutation. There were no significant differences in clinical background, including age, sex, BMI, comorbidities, or history of thrombosis, between the positive and negative groups. The blood count and coagulation parameters did not differ significantly between the two groups. Among the 11 patients in the positive group, 9 had embolic stroke and 2 had thrombotic stroke. Embolic stroke of undetermined source (ESUS) was more frequently observed in the positive group than in the negative group (45 vs. 13%; p=0.002). Stroke severity and outcomes did not differ between the two groups. DiscussionApproximately 1% of patients with acute ischemic stroke or TIA carry the JAK2 V617F mutation despite normal blood counts. Of the 11 mutation-positive patients, nine (82%) exhibited embolic imaging features and five (45%) met the ESUS criteria, whereas other clinical characteristics did not differ significantly from the mutation-negative group.