A NEW HEREDITARY CAUSE OF PORTAL-VEIN THR OMBOSIS - ABNORMAL RESISTANCE, TO ACTIVATED PROTEIN-C BY ARG506-]GIN MUTATION IN THE GENE FOR FACTOR-V

We report 2 cases of portal vein thrombosis associated with a single p oint mutation in the factor V gene that replaces arginine in residue 5 06 with glutamine. This mutation induces abnormal resistance to antico agulant activity of activated protein C and increases the risk of deep vein thrombosis. Both patients had a personal and familial history of deep vein thrombosis. Intraabdominal neoplasia or infection, myelopro liferative disorder, antiphospholipid syndrome, paroxysmal nocturnal h emoglobinuria and coagulation inhibitor deficiency (antithrombin, prot eins C and S) were excluded by exhaustive investigation. However, an a bnormal resistance to activated protein C was found, and DNA analysis showed the factor V Arg506 to Gin mutation in both cases. Anticoagulan t treatment was begun. A study of family history made in one case, sho wed the same genetic disease in one of the relatives. Resistance to ac tivated protein C with factor V gene mutation should be investigated i n patients with portal vein thrombosis. A study of family history, and anticoagulant treatment are justified for symptomatic patients.