Thus, this mutation is now recognised as a diagnostic cornerstone.26 The close relationship between MPN and splanchnic vein thrombosis has been confirmed by the current one-third prevalence of the JAK2 V617F mutation among patients with BCS and EHPVO (Tables 1-2).27,28 Patients with splanchnic vein thrombosis that show no additional signs of haematologic disease other than the JAK2 V617F mutation at the time of thrombosis have an overt MPN development rate as high as 52% during the follow-up.28 The gene discussed is JAK2; the disease is myeloproliferative neoplasm.