How are the factor V deficiencies differentiated and treated?

Updated: Oct 06, 2020
  • Author: Irene S Pakos, DO; Chief Editor: Perumal Thiagarajan, MD  more...
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In 1998, Girolami et al proposed an updated classification that separated factor V deficiencies into those that cause hemorrhage and those that cause thrombosis. [58] Their classification of hemorrhagic disorders included (1) homozygous and heterozygous "true" factor V deficiency and (2) combined factor V and factor VIII deficiencies.

The factor V Q506 mutation is found in 20-60% of white patients with thrombosis. Its prevalence varies between countries; it is highly prevalent (up to 15%) in Scandinavian populations. [73]

In a study of 51 families with factor V Leiden, Samama et al reported that the factor V mutation was present in 84 of 125 family members (81 heterozygous, 3 homozygous). Venous thrombosis was observed in 17 of the 84 family members with the mutation, and in 6 of the 41 with a normal aPCR test finding and no mutation. An associated protein C or protein S deficiency was present in 5 families (10%). [74]

The most frequent clinical manifestations of aPCR or factor V Leiden deficiency are SVT or DVT and/or pulmonary embolism and thrombosis at an unusual site (eg, cerebral, mesenteric, or central retinal vein). A causal relationship is frequently difficult to demonstrate. A precipitating factor was observed in 84% of cases, and a recurrent thrombotic episode occurred in 50% of those affected in Samama et al's study. The risk of thrombosis associated with pregnancy was high in the postpartum period, especially in homozygous women. In homozygous patients, markers of coagulation activation are frequently elevated in those who are untreated. In heterozygous true factor V deficiency, both activity and antigen are about 50% of normal. [75]

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