Clinical and physiologic studies of two siblings with prekallikrein (Fletcher factor) deficiency.

Two siblings with hereditary Fletcher factor (prekallikrein) deficiency were studied for alterations of fibrinolysis, platelet function, skin inflammatory responses, permeability factor (PF/dil) formation and leukocyte chemotaxis. In vivo stimulation of fibrinolytic activity was normal; the bleeding time and platelet functions (adhesivity, aggregation, release reaction) were also normal. Both immediate (wheal-flare reaction to histamine, bradykinin, prostaglandin E1, physical agents) and delayed sensitivity skin test reactions were within normal limits. Migration of subjects' leukocytes to attractants in skin windows and in Boyden-type chambers was the same as that of control leukocytes. Serum complement components were essentially normal. One subject's leukocytes showed normal tissue factor production on stimulation by endotoxin, although prekallikrein deficiency did impair the endotoxin-stimulated generation of serum procoagulant activity. PF/dil caused increased vessel permeability in human skin; in vitro generation of PF/dil required both the Hageman factor and prekallikrein. The Fletcher factor-deficient subjects responded in a normal manner to PF/dil. Based on the Fletcher factor-coagulation assay, the biologic half-disappearance time of prekallikrein (after the transfusion of normal plasma in one of the subjects) was estimated at 35 hours. Therefore, these studies suggest that severe prekallikrein (Fletcher factor) deficiency in man is not associated with any clinically significant impairment in hemostasis, fibrinolysis, inflammatory responses or leukocyte function.