A Hitherto Undescribed Plasma Factor Acting at the Contact Phase of Blood Coagulation ( Flaujeac Factor )

This paper reports an asymptomatic coagulation defect responsible for an abnormality at the contact phase of blood coagulation in vitro, distinct from Hageman factor and Fletcher factor deficiencies. Coagulation studies in a 50-yr-old French woman without bleeding tendency revealed the following results: whole-blood clotting time in glass tubes and activated partial thromboplastin time with kaolin and ellagic acid were greatly prolonged; one-stage prothrombin was normal; no circulating anticoagulant was detected, and the infusion of normal plasma corrected the coagulation defect with an estimated half-life of 6.5 days; the levels of factor VIII, IX, XI, and XII were normal; mutual correction was obtained with a Fletcher factor-deficient plasma; the level of whole complement was normal. Studies of the contact phase of blood coagulation and contact-induced fibrinolysis showed the same abnormalities as in Hageman factorand Fletcher-deficient plasmas. These results indicate that the patient’s plasma is deficient in a previously undescribed coagulation factor, which participates in the initial stage of the blood coagulation precess in vitro. Family studies revealed consanguinity in the prepositus’ parents. The assay of this newly described factor in the prepositus’ children revealed a partial defect, compatible with a heterozygous state, in three of the four tested children. This indicates a recessive inheritance of this new blood coagulation defect.