Hematology: Factor V Leiden

Definition

• Mutation Causes Factor V (5) to Become Resistant to Activated Protein C (APC)
  • APC Normally Inhibits Factor V
  • Resistance Induces Hypercoagulability
• The Most Common Congenital Hypercoagulability Disorder
• Prevalence:
  • Heterozygous Mutation: 2.0-7.0%
  • Homozygous Mutations: 0.2-0.5%

VTE Risk

• Lifetime Risk for VTE: 5-10%
• Increased Risk:
  • Thrombophilic Family
  • Concurrent Prothrombin G20210A Mutation (Referred to as a Double/Combined Heterozygote)
  • Homozygous Mutation
• Risk for Recurrent VTE After a First VTE is Only Modestly Increased

Diagnosis

• Diagnosis: APC Resistance Assay (Functional Coagulation Test) or DNA Testing (Genetic Test)
• 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: Prothrombin G20210A
  • *See Hematology & Oncology: Antithrombin-III Deficiency
  • *See Hematology & Oncology: Protein C Deficiency
  • *See Hematology & Oncology: Protein S Deficiency

Management

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