However, a recent study showed an increased risk of vascular access thrombosis in the carriers of the mutant FV (G1691A and A4070G) polymorphisms [24], and an Indian study demonstrated that the factor V Leiden mutation is the major causative factor in Budd–Chiari syndrome and portal vein thrombosis in the adult group, but it was not a major contributing factor in the pediatric group [25]. The gene discussed is F5; the disease is hepatic veno-occlusive disease.