Protein C deficiency
Protein C deficiency is a hypercoagulable state due to reduced activity or an absolute deficiency of protein C, an anticoagulant protein. Protein C deficiency increases the risk of venous thrombosis.
The prevalence of protein C deficiency in the general population is around 1 per 200-500 people . Protein C deficiency may be present in around 2-5% of all patients with venous thromboembolism.
Homozygous cases usually present in neonates with purpura fulminans. Presentation in heterozygous cases is variable and can range from varying degree of venous thromboembolism to embolic complications. The risk of venous thromboembolism in heterozygotes is seven times higher than in the general population .
Arterial thrombotic complications sometimes been very rarely reported .
Protein C is converted to activated protein C by thrombin. Activated protein C then cleaves and inactivates activated factor VIII and V protein therefore inhibiting factor X activation and further thrombin formation. The presence of the cofactor protein S is also important for protein C activation .
Most cases are genetic however some may be due to an acquired deficiency from:
- warfarin use
- liver disease
- disseminated intravascular coagulation
- vitamin K deficiency
Type I deficiency
- quantitative deficiency of protein C
- variable phenotypic presentation ranging from recurrent thromboembolism to asymptomatic
- autosomal inheritance usually
- due to mutations in PROC gene which encodes protein C
- Estimated penetrance of protein C deficiency can vary from as low as 20-30% to as high as 75%
Type II deficiency
- decreased functional activity of protein C but normal levels
No specific radiographic features while imaging is mainly around evaluating thomrobotic and embolic complications.
Treatment and prognosis
Treatment depends on the severity of the protein C deficiency. In severe cases of protein C deficiency, protein C concentrate and fresh frozen plasma has historically been used. However, some cases are now treated with novel oral anticoagulants (e.g. rivaroxaban) .