Factor-XII Congenital Deficiency. A New Family Study

Evaluation of the clotting defect in a factor XII-deficient kindred

A family with factor XII severe congenital deficiency is described. Factor XII activity and factor XII antigen were both undetectable in the propositus plasma; levels of FXII:C and FXII:Ag were intermediate in heterozygotes. Plasma prekallikrein activity was low in the propositus, whereas normal levels of antigen could be found, suggesting a defect of kallikrein activation due to factor XII deficiency.

[Congenital factor XII deficiency: a rare cause of increased activated cephalin time]

The fortuitous detection of an increased activated cephalin clotting time is often dependent on defects of the blood-clotting factors synthesized by the liver, haemophilia or von Willebrand's disease, circulating anticoagulants or specific deficiencies of various factors necessary for blood-clotting mechanisms. Much more rarely, it may be due to an isolated Hageman factor defect. This deficiency does not lead to an increased bleeding tendency and surgery has proved surprisingly uneventful. On the other hand, thromboembolic events may appear. Being and inherited disease with autosomal recessive transmission, the discovery of Hageman factor deficiency must lead to a complete family investigation.