Research has shown that 30–50% of patients with splanchnic-vein thromboses associated with Budd-Chiari syndrome (including portal-venous and hepatic-vein thrombosis) harbour a somatic mutation of the JAK2 gene (JAK2 V617F) that constitutively activates JAK2 kinase (Kiladjian et al, 2008). The gene discussed is JAK2; the disease is hepatic vein thrombosis.