Hereditary heparin cofactor II deficiency and thrombosis: report of six patients belonging to two separate kindreds.

We describe six patients belonging to two families with congenital heparin cofactor II deficiency (HC II). The affected members had low levels of HC II antigen and activity, and no abnormalities in HC II electrophoretic mobility were detected in the presence of heparin or dermatan sulphate during the first migration of crossed immunoelectrophoresis. These data suggested that patients had a type I (true) HC II deficiency. The association of thrombotic manifestations with congenital HC II deficiency has not been completely clarified. In these two families, thrombotic events occurred in two out of six affected members. In addition, there was a high incidence of spontaneous abortion in the affected females. Finally, the association of congenital HC II deficiency with angiomatosis was also observed in one patient.