Constitutional dysfunction of heparin cofactor II with a tendency for venous thrombosis

: Simultaneous determination of heparin cofactor II (HC II) immunologically as antigen (HC II:Ag) and functionally as heparin cofactor (H-HC II) and as dermatan sulfate cofactor (DS-HC II) renders possible a distinction between quantitative and qualitative deficiencies. The usefulness of these methods is demonstrated in the light of a family with several heterozygotes of quantitative HC II deficiency and two unrelated heterozygote men with defective dermatan sulfate cofactor function (DS HC II) and normal HC II:Ag and H-HC II.