Occult JAK2+ Myelofibrosis Presenting With Splanchnic Vein Thrombosis

Splanchnic vein thrombosis (SVT) is a rare manifestation of venous thromboembolism within the portal, mesenteric, hepatic, and/or splenic veins. Major risk factors include abdominal cancer, cirrhosis, and myeloproliferative neoplasms (MPNs). Myeloproliferative neoplasms can be associated with JAK2 V617F mutations, representing unique thrombotic risk factors. Discussed below is an atypical case of occult JAK2+ myelofibrosis with normal blood counts presenting as SVT, which would have been missed without high clinical suspicion. This case demonstrates the need to test for thrombophilia syndromes, JAK2, and occult MPNs in otherwise unexplained SVT to optimize treatment and prevent life-threatening manifestations such as portal hypertension sequelae and cirrhosis.