RESUMEN
The Budd-Chiari Syndrome (BCS) and the splanchnic vein thrombosis are characterized by hepatic venous outflow obstruction, generally due to venous thrombosis. These rare diseases are usually caused by multiple concurrent factors, including acquired and inherited thrombophilias. Since the diagnosis of myeloproliferative neoplasms (MPNs) is often difficult in patients with BCS and splanchnic vein thrombosis because of spleen enlargement, secondary pancytopenia and bleeding disorders, recent observations have included in the diagnostic work-up the analysis of the JAK2 mutation. The revision of several recent reports clarify the importance of the JAK2V617F detection in the diagnostic work-up of the BCS and splanchnic vein thrombosis, allowing the demonstration of masked MPNs among these cases that may benefit, in the near future, of target molecular therapies directed toward the JAK2 mutation.