Primary Budd–Chiari syndrome (BCS) is a spontaneously fatal disease characterized by an obstruction of the hepatic venous outflow tract due to thrombosis or a primary disease of the venous wall.
The primary form of BCS is extremely rare, with the prevalence estimate (1 case per 1 million persons per year) falling well below the threshold of 2 cases per 10,000 for rare diseases.
The median age at diagnosis is 35 to 40 years. The two sexes appear to be equally affected. Recent advances have changed our understanding of this disease, as well as the outcomes. In this review, we confine our discussion to primary BCS.