Congenital Abnormality of the Prothrombin Molecule (Factor II) in Four Siblings: Prothrombin Barcelona

A family is described in which four siblings suffer from an unusual hemorrhagic syndrome. In the patient’s plasma, the prothrombin level is only 5% of normal by standard clotting assay and 100% both by staphylocoagulase and immunochemical assays. Results of further investigations in these patients and their family are in favor of a genetic defect of the prothrombin molecule transmitted as a recessive autosomal trait. This abnormal prothrombin is slowly activated by prothrombinase and its electric charge differs from that of normal prothrombin.