Incidence of the JAK2 V617F mutation among patients with splanchnic or cerebral venous thrombosis and without overt chronic myeloproliferative disorders

Background: Thrombosis of splanchnic or cerebral veins is a typical manifestation of polycythemia vera (PV) or essential thrombocythemia (ET). The recently identified Janus kinase 2 (JAK2) V617F somatic mutation is closely related to chronic myeloproliferative disorders (CMD). Objective: To assess the incidence of the JAK2 V617F mutation among patients with splanchnic or cerebral venous thrombosis with or without overt CMD. Patients and methods: We searched for the mutation in 139 adult patients (> 18 years old) with thrombosis of hepatic veins (HVT, n = 15), or extrahepatic portal vein (PVT) and/or mesenteric vein (MVT) (n = 79), or cerebral veins (CVT, n = 45). Only 19 patients fulfilled criteria for diagnosis of PV (n = 8) or ET (n = 11) at the time of thrombosis: four had HVT, 11 PVT and/or MVT, and four CVT. Results: The JAK2 V617F mutation was found in 94.7% [95% CI 75.3-99.0] of the patients with overt CMD at the time of thrombosis, in 21.5% (95% CI 13.8-31.7) of the patients with abdominal venous thrombosis and without overt CMD, and in 4.8% (95% CI 1.3-16.1) of the patients with CVT and without overt CMD. Among the patients without overt CMD or thrombophilia and with unprovoked thrombosis, 29.4% (95% CI 16.8-46.1) with splanchnic venous thrombosis and 42.8% (95% CI 24.4-63.4) with PVT had the JAK2 V617F mutation. Conclusions: A substantial proportion of patients with splanchnic venous thrombosis and a small, but significant, number of patients with CVT can be recognized as carriers of the JAK2 V617F mutation in the absence of overt signs of CMD. The clinical significance of such findings deserves further investigation.