In the article we analysed the difficulties of differential diagnosis of portal hypertension, considers a clinical case that illustrates the presented theoretical material. In the presented clinical observation, the patient’s disease was manifested by bleeding from the varicose veins of the esophagus. In most cases, portal hypertension syndrome in practicing clinicians is associated with liver cirrhosis, however, it is necessary to remember about the possibility of developing subhepatic portal hypertension, in particular as a result of the formation of portal vein thrombosis. If there are signs of portal hypertension, it is necessary to specify the level of obstruction to blood flow, that is, the form of portal hypertension (subhepatic, hepatic, suprahepatic). Often, portal vein thrombosis can be formed due to undiagnosed blood diseases that occur without any clinical symptoms. The provided clinical example demonstrates a case of portal hypertension in the outcome of a chronic form of myeloproliferative syndrome. Portal cavernoma is quite rare and it is formed due to multiple small-diameter venous structures that gradually replace the occluded vessel with a system of collaterals proximal and distal to the portal vein thrombosis site. In the formation of the diagnosis the main are radiation research methods, but the conclusions should be considered only in conjunction with the clinical evidence. The clinical case is interesting because a large cavernoma of the portal vein in a patient with subhepatic portal hypertension was regarded as a «solid formation» according to magnetic resonance tomography. According to the literature data, cavernous transformation has an external similarity to the tumor process, which expands the range of differential diagnosis and requires the exclusion of oncological formations.