The annual thrombotic risks are variable and depend on the underlying thrombophilia.^[1]

• Factor V Leiden and Prothrombin G20210A: If left untreated, the annual incidence of incident thrombosis in asymptomatic patients is low (<0.06%). However, the occurrence of recurrent thrombosis can not be predicted in such inherited thrombophilias. ^[2][3][4]
• Protein C, Protein S, and Antithrombin deficiencies: These conditions carries an increased risk for recurrent thrombosis in untreated patients. ^[3][5]
• Oral contraceptives, hormone replacement therapy, and pregnancy can significantly increase thrombotic risk in patients with underlying thrombophilia.^[6]
• Certain high risk thrombophilias require indefinite anticoagulation. However, such patients on preventive oral anticoagulant therapy for venous thromboembolism still carries the annual incidence of significant bleeds of ~2-3%.^[7]

• The primary complication of thrombophilia is the development of blood clots, also known as thrombus formation.
• The most common complications of thrombophilia are as follows: ^[1][2][6]
  • Deep vein thrombosis
  • Pulmonary embolism
  • Postthrombotic syndrome (PTS) with chronic venous ulceration (CVU) ^[8]

Table 1: The risk of future thrombosis in patients with thrombophilia:

Table 2: The effect of concurrent hormone exposure on incident thrombosis and thrombotic risk in patients with underlying thrombophilia:

• The prognosis depends on the underlying thrombophilia as each disorder has a different associated thrombotic risk (Table 1 and 2).
• Thrombophilias associated with the development of multiple or atypical clots, arterial thrombosis, or life-threatening thrombosis carries worse prognosis which are as follows:
  • Antiphospholipid Syndrome
  • Paroxysmal nocturnal hemoglobinuria
  • Antithrombin III deficiency
  • Factor V Leiden homozygosity
• High risk thrombophilic conditions require consideration for lifelong anticoagulation under the supervision of an expert consultant.
  • Antiphospholipid Syndrome
  • Paroxysmal nocturnal hemoglobinuria
  • Recurrent thrombosis regardless of underlying thrombophilia
  • History of life-threatening thrombosis or atypical locations
  • Malignancy with history of thrombosis