Abstract
Four cases with congenital F. XII deficiency from a family were reported. A 38-yrs-old female (case 1) was found to have a markedly prolonged kaolin-activated partial thromboplastin time in preoperative coagulation tests. The F. XII clotting activity (F. XII-Act) was less than 1% of normal and F. XII antigen (F. XII-Ang) measured by radioimmunoassay was less than 0.1%.
Case 2 (her mother, 74-yrs-old), case 3 (her sister, 57-yrs-old) and case 4 (her brother, 30-yrs-old) showed 15, 22 and 14% of F. XII-Act and 22, 22 and 24% of F. XII-Ang respectively. None of them had had a hemorrhagic tendency, and appendectomy in case 1 and cesarean section in case 3 were quite uneventful. Case 1 was supposed to be a homozygous state and the others heterozygous traits. The levels of Fletcher and Fitzgerald factors, and of complements (CH50, C3 and C4) were normal in case 1. The levels of plasmin, plasminogen and SK-activated plasmin measured by the method of fibrin plate were normal and inhibitors to fibrinolysis were also within normal range in all cases.
In contrast, kaolin-activated euglobulin lysis time (K-ELT) was markedly prolonged in case 1 and moderately in the others in proportion to their F. XII activities.
It was shown that the prolonged K-ELT of plasma from case 1 was remarkably corrected by addition of a small amount of normal plasma and that K-ELT of normal plasma became shortened according to the increase of incubation time of the plasma with kaolin, although that of patient's plasma (case 1) was not affected by contact with kaolin and remained prolonged.
These results suggest that F. XII plays an important role in the initiation of intrinsic pathway not only of blood coagulation but also of fibrinolysis. F. XII deficient cases reported in Japan by 1976 were summarized briefly.
