- INTRODUCTION: Splanchnic venous thrombosis (SVT) has varied etiology with Philadelphia-negative myeloproliferative neoplasms (MPNs) being the most frequent underlying prothrombotic factor. Hematological indices often remain within normal range because of portal hypertension and its sequelae, causing diagnostic challenges. The high frequency of JAK2 mutation among patients with SVT reinforces the diagnostic utility of JAK2V617F testing. CASE REPORT: We report a case of a 62-year-old black man with progressive abdominal swelling and features of decompensated chronic liver disease found to have SVT-portal vein thrombosis and how JAK2 V617F was useful in unmasking an underlying myeloproliferative neoplasm. CONCLUSION: A high index of suspicion for an underlying prothrombotic factor is critical for patients presenting with thrombosis in unusual sites. This is useful in prognostic stratification and patient outcomes. JAK2 mutation screening is now part of the standard diagnostic workup in SVT.