What is hypoprothrombinemia?

Updated: Jun 16, 2021
  • Author: J Nathan Hagstrom, MD; Chief Editor: Cameron K Tebbi, MD  more...
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Prothrombin (factor II of the coagulation cascade) is a critical protein in hemostasis. Decreased levels of prothrombin can lead to a bleeding diathesis. The most common manifestations of hypoprothrombinemia are associated with mucocutaneous bleeding. However, hemorrhage involving deep structures can be observed with severe prothrombin deficiency.

Hypoprothrombinemia may be acquired or inherited. Acquired forms may be secondary to decreased production or increased consumption. Acquired isolated hypoprothrombinemia is usually autoimmune and associated with the lupus anticoagulant. A relatively common form of acquired hypoprothrombinemia is vitamin K deficiency. Levels of other vitamin K–dependent procoagulant factors (factors VII, IX, and X) and anticoagulant factors (protein C and protein S) are also decreased in vitamin K deficiency.

Inherited prothrombin deficiency is rare. [1] Two phenotypes are described: hypoprothrombinemia (type I deficiency) and dysprothrombinemia (type II deficiency). In type I deficiency, prothrombin levels and prothrombin activity are reduced. In type II deficiency, prothrombin activity is reduced, but prothrombin levels are borderline or in the reference range. Both disorders are autosomal recessive. The prothrombin gene is found on chromosome 11.

Heterozygotes for prothrombin deficiency have factor II levels of 30-60% of the reference range. Heterozygotes are usually asymptomatic, although a study by Girolami et al found that mean prothrombin activity was lower in patients who were heterozygous for prothrombin deficiencies than in controls (0.49 IU/dL vs 0.91 IU/dL, respectively), with bleeding manifestations found in 31.8% of the heterozygous individuals, compared with 6.8% of controls. [2]

Compound heterozygotes who have type I and type II mutations are occasionally reported.

The treatment of hypoprothrombinemia depends on the underlying etiology. Plasma-derived products that contain factor II are available. Vitamin K-1 (phytonadione) is used to treat vitamin K deficiency as well as warfarin overdose. In autoimmune disease, treatment is not entirely straightforward, and immunosuppressive therapy is used in severe cases.

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