Hereditary protein S deficiency in a large New Jersey kindred

Protein S is a vitamin K-dependent anticoagulant protein that serves as a cofactor for activated protein C. Deficiency of protein S has been associated with recurrent thrombotic events. To characterize better the risks of thrombosis in protein S deficiency, we studied 62 members in a large kindred.

All members were evaluated by a thorough clinical history. Plasma samples were assayed for total protein S antigen and protein S activity. Upper and lower extremity venous duplex examinations were performed in the majority of adult members.

Twenty-six (40%) of the 62 family members were classified as deficient on the basis of either low total protein S antigen levels or low protein S functional activity. Five members deficient in protein S had 16 venous thrombotic events. In all members the onset of thrombotic events occurred after 19 years of age, with a tendency for recurrence. Three lower extremity deep venous thromboses that had been occult previously were first diagnosed on surveillance duplex scanning. Only one member whose protein S level was not deficient had a single episode of superficial thrombophlebitis.

Our findings in this large kindred confirm an autosomal-dominant inheritance pattern. Thrombotic events occurred after the age of 19 years in affected individuals and tended to be recurrent. The diagnosis of protein S deficiency is based on functional and immunologic plasma assays. In this study venous duplex scanning proved to be a useful diagnostic adjuvant.