Pancytopenia With Hypocellular Bone Marrow Revealing Extrahepatic Portal Venous Obstruction and Cavernous Transformation in a Child: A Case Report of a Diagnostic Challenge.

Extrahepatic portal venous obstruction (EHPVO) is a leading cause of prehepatic portal hypertension in children, particularly in developing countries. While upper gastrointestinal bleeding is the most common presentation, EHPVO may rarely manifest predominantly with hematological abnormalities due to hypersplenism, posing a diagnostic challenge and mimicking primary bone marrow disorders. We report a 13-year-old female child who presented with pancytopenia, splenomegaly, and easy fatigability, without a history of gastrointestinal bleeding or liver disease. Initial evaluation suggested a primary hematologic disorder, and bone marrow aspiration revealed a hypocellular marrow without malignant infiltration. Extensive workup excluded nutritional, infectious, autoimmune, and malignant causes of pancytopenia. Subsequent abdominal imaging demonstrated non-visualization of the main portal vein with multiple periportal collateral vessels and hepatopetal flow, consistent with cavernous transformation of the portal vein secondary to chronic extrahepatic portal venous obstruction. Upper gastrointestinal endoscopy revealed grade III esophageal varices, which were managed with endoscopic variceal ligation and initiation of non-selective beta-blockers. This case illustrates an uncommon but clinically important presentation of pediatric EHPVO, in which hypersplenism leads to pancytopenia and secondary bone marrow suppression, closely mimicking primary marrow failure. Recognition of this pattern is crucial to avoid misdiagnosis and unnecessary investigations. Imaging, particularly Doppler ultrasonography, plays a pivotal role in establishing the diagnosis. EHPVO should be considered in the differential diagnosis of pancytopenia with splenomegaly in children, even in the absence of overt gastrointestinal bleeding. Early recognition through appropriate imaging can guide timely management and prevent complications of portal hypertension.