24th July 2024

Protein S deficiency

Protein S works synergistically with protein C to inactivate factor V. As with protein C, a deficiency of protein S leads to a prothrombotic state. It also is dependent on vitamin K. Conditions such as nephrotic syndrome, liver failure, pregnancy and oral contraceptive use lead to lower levels of protein S.

Free protein S levels can aid diagnosis, though can be complicated by the fact that these vary within the population.

If a patient has confirmed VTE and protein S deficiency the choice of anticoagulant does not differ from regular management.