Rare hereditary thrombophilia

Rare hereditary thrombophilia (Orphanet code 217454) is a group of uncommon inherited disorders of the coagulation system that predispose affected individuals to an increased risk of abnormal blood clot formation (thrombosis), particularly venous thromboembolism (VTE). This category encompasses rarer genetic deficiencies in natural anticoagulant proteins, including antithrombin deficiency, protein C deficiency, and protein S deficiency, as well as other uncommon inherited coagulation abnormalities that go beyond the more frequently encountered thrombophilias such as Factor V Leiden or prothrombin G20210A mutation. The vascular system is primarily affected, with clots most commonly forming in the deep veins of the legs (deep vein thrombosis) and potentially traveling to the lungs (pulmonary embolism). Other affected vascular beds may include cerebral, mesenteric, or portal veins. Some patients may also experience recurrent pregnancy loss or other obstetric complications due to placental thrombosis. Clinical manifestations typically include swelling, pain, and redness in affected limbs, shortness of breath in cases of pulmonary embolism, and in severe forms (particularly homozygous protein C or protein S deficiency), neonatal purpura fulminans — a life-threatening condition presenting in the newborn period with widespread skin necrosis and disseminated intravascular coagulation. The age of onset is variable; heterozygous individuals may remain asymptomatic or develop their first thrombotic event in young adulthood, often triggered by additional risk factors such as surgery, immobilization, oral contraceptive use, or pregnancy. Homozygous or compound heterozygous forms tend to present much earlier, sometimes in the neonatal period. Treatment involves acute anticoagulation therapy (typically heparin followed by oral anticoagulants such as warfarin or direct oral anticoagulants) for thrombotic events, and long-term or lifelong anticoagulation may be recommended for individuals with recurrent thrombosis or severe deficiency states. In neonatal purpura fulminans, replacement therapy with protein C concentrate or fresh frozen plasma may be life-saving. Genetic counseling is recommended for affected families. Management is individualized based on the specific deficiency, severity, and personal and family thrombotic history.

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