Constitutional heparin co-factor II deficiency associated with recurrent thrombosis

The family of a 36-year-old man with recurrent deep venous thrombosis and heparin co-factor II (HC II) deficiency was investigated for this deficiency. The deficiency was inherited as an autosomal dominant trait. 4 members of the family had low HC II levels but only the proband had a history of thromboses; however, 2 of 4 affected were only 14 and 23 years old. The deficiency did not affect the anticoagulant action of heparin, with which the patient was treated.