SummaryIn order to assess the clinical implications of hereditary F XII deficietrcy, all available members of Swiss families with F XII deficiency were investigated. Based on the F XII: C values and the family pedigree, the 74 subjects, aged 8-–82 years, were classified as homozygotes/double heterozygotes for F XII deficiency (n = 18), as obligatory (n = 20) or possibly (n = 25) heterozygotes, respectively, and as norrnals (n = 11). None of the 18 subjects with F XII: C <0.01 U/ml and only one possibly heterozygous woman had an abnormal bleeding tendency, confirming the notion that Hageman trait generally does not result in a hemorrhagic diathesis. Two of the 18 subjects with severe F XII deficiency had suffered from venous thromboembolic disease at age <40 years. One heterozygous woman had a leg ulcer probably due to venous thrombosis. Thus, whereas homozygous F XII deficiency may be associated with an increased risk for venous thromboembolic disease, partial F XII deficiency is not, by itself, a strong risk factor for thrombosis.Where as 17 of the 18 subjects with F xII : C <0.01 U/ml had no detectable F XIL Ag, one cross reacting material-positive F XII deficient subject (F XII:Ag = 0.11 U/ml) was identified. The dysfunctional F XII, present in this subject's plasma and tentatively called F XII Bern, is the fourth abnormal F XII molecule identified so far.

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The appearance of fibrinopeptide A (FPA) in plasma indicates that factor VIII has been at least partially activated; consequently, we asked the following questions: (1) Is the FPA content of single donor plasma influenced by the method of blood collection? (2) Does a high FPA content of the starting fresh frozen plasma impair the quality of factor VIII preparations? Using a modified procedure adapted to the assay of large series of samples, we surveyed the FPA content of normal donor plasma. Our results show that the FPA content of donor plasma depends strongly on the quality of blood collection. Improved mixing of the anticoagulant with the blood led to a drastic reduction of the FPA content of the plasma. Furthermore, two lots of factor VIII concentrates produced from FPA-poor plasma showed significant improvement in stability and solubility.

Human serum glycine-rich β-glycoprotein was genetically typed by agarosegel electrophoresis, followed by immunofixation. Analysis of a Swiss and an Italian population revealed a difference in the gene frequencies.