Congenital prekallikrein deficiency.

The congenital deficiency of prekallikrein (PK) is a rare condition in which there is a peculiar discrepancy between a severe in vitro defect and absence of bleeding. The gene controlling PK synthesis is located on chromosome 4 and consists of 14 exons and 15 introns. Only approximately 80 cases of PK deficiency have been described in the literature.

The clinical significance of the lack of arterial or venous thrombosis in patients with congenital prothrombin or FX deficiency.

Several reports have dealt with the occurrence of both arterial and venous thrombosis in patients with haemophilia A, haemophilia B, and von Willebrand disease. Similar thrombotic events have been occasionally reported also in rare congenital coagulation disorders, particularly in fibrinogen or FVII deficiencies. On the contrary no sure venous or arterial thrombotic event has ever been reported in congenital prothrombin or Factor X deficiency.