Hematology: Protein S Deficiency

Definition

• Definition: Deficiency in Protein S (< 60-65%)
  • Normally Protein S is a Cofactor for Activated Protein C (aPC) to Inhibit Factors Va & VIIIa
• Diagnosis the Most Difficult Due to the Most Wide Variation in Circulating Levels
• Prevalence: 0.1%

Effects

• Increased Risk for VTE (Odds Ratio 3)
• May Have an Increased Risk for Warfarin-Induced Skin Necrosis (More Typically Associated with Protein C Deficiency)

Diagnosis

• Diagnosis: Free Protein S Level
• Indication for Testing:
  • Thrombophilic Family (Strong Family History of VTE)
  • VTE at a Young Age (< 50 Years)
  • VTE in an Unusually Location (Portal/Hepatic/Mesenteric/Cerebral)
  • Recurrent VTE
• In General, If Testing Should Also Test for Other Inherited Thrombophilias
  • *See Hematology & Oncology: Factor V Leiden
  • *See Hematology & Oncology: Prothrombin G20210A
  • *See Hematology & Oncology: Antithrombin-III Deficiency
  • *See Hematology & Oncology: Protein C Deficiency

Management

• VTE Treatment: Anticoagulation – Similar to the General Population
• VTE Prevention: Generally Can Avoid Routine Chronic Anticoagulation Unless Otherwise Indicated or High-Risk