Masked polycythaemia vera presenting with extensive splanchnic venous thrombosis and mesenteric ischaemia.

Splanchnic venous thrombosis (SVT) is a potentially catastrophic manifestation of polycythaemia vera (PV). We report a woman in her 60s with masked PV who had been managed for 5 years with intermittent phlebotomy and aspirin without haematology referral, molecular testing or cytoreductive therapy. Chronic iron deficiency masked erythrocytosis, delaying diagnosis. She presented with extensive thrombosis involving the portal, splenic and superior mesenteric veins complicated by mesenteric ischaemia requiring exploratory laparotomy, jejunal resection and ileostomy. Bone marrow biopsy and JAK2 V617F testing confirmed PV. Therapeutic anticoagulation was initiated with enoxaparin and subsequently transitioned to apixaban, while hydroxyurea achieved sustained haematologic control. Interval imaging demonstrated thrombus regression with persistent cavernous transformation. Given ongoing portal hypertension, oesophageal varices, occasional mild ostomy bleeding and low body weight, anticoagulation was continued indefinitely at reduced intensity with apixaban 2.5 mg twice daily. At 21-month follow-up, the patient remained free of recurrent thrombosis and major bleeding.