Successful pregnancy in a patient with factor V deficiency: case report and review of the literature.

Thromb Haemost 2006; 95: 896–7 The clotting factor now known as factorV (FV) was first described in 1908 (1), and a deficiency of this factor was first described by Owren as parahaemophilia in 1947 (2). FV is predominantly produced in the liver and to a lesser degree by the megakaryocytes. Circa 80% of FV circulates in the plasma while 20% is stored in platelets. Following α-granule release upon platelet activation, platelet FV can presumably bind immediately to surface receptors optimising prothrombinase complex activity (3). The relationship between plasma FV and platelet FV and their relative significance is to date not fully understood, but FV expression in either platelets or plasma was proven to be sufficient for basal haemostasis in mice (4). FV deficiency is a rare disease with an incidence of 1.10–6 (5, 6, 20-24). It is an autosomal recessively inherited disorder in which the lack of factor V activity impairs clotting. Heterozygous patients show a variable expression with a mild bleeding tendency in 10% of the cases (7), whereas homozygous patients usually present with moderate clinical manifestations of epistaxis, menorrhagia and haemorrhages after trauma (8). There seems to be a poor correlation between plasma factor V levels and clinical phenotype (8), and different opinions exist as to the necessary level of circulating FV for adequate haemostasis. Target FV activity levels during treatment are mainly based on clinical experience (9). Relatively few reports on the subject of factor V deficiency and pregnancy can be found in the medical literature, and these are mainly sporadic case reports (10–18) and three reviews (3, 20, 21).