Factor V (FV) is a crucial regulator of hemostasis, functioning as both a procoagulant and an anticoagulant glycoprotein within the coagulation cascade. In plasma, FV exists as an inactive precursor, which is activated by thrombin or factor Xa into its procoagulant form, FVa, contributing to the formation of the prothrombinase complex. Additionally, FV isoforms generated via alternative splicing, notably FV-short, exhibit anticoagulant properties by interacting with tissue factor pathway inhibitor-alpha (TFPIα), thus playing a role in regulating blood coagulation.

Factor V deficiency is a rare condition characterized by a bleeding tendency, with a prevalence of approximately 1:1,000,000 in the general population. Clinical presentations can range from mild mucosal bleeding to severe hemorrhagic events. However, in rare cases, thrombotic complications may also occur, highlighting the heterogeneous clinical spectrum of FV deficiency.

In this case report, we will discuss a patient who presented with deep vein thrombosis (DVT) and was diagnosed with FV deficiency.

A 43-year-old female presented to the emergency department of Dicle University Hospital on July 21, 2024, with complaints of pain and swelling in her left leg. Physical examination and lower extremity venous Doppler ultrasonography revealed an echogenic thrombus within the distal iliac, femoral, popliteal, and proximal deep crural veins, leading to a diagnosis of deep vein thrombosis (DVT).

Initial coagulation tests showed prolonged prothrombin time (PT) of 246 seconds, INR of 2.21, and activated partial thromboplastin time (APTT) of 38.2 seconds, with PT being more significantly prolonged. The complete blood count was normal. The patient was admitted to the cardiovascular surgery clinic for thrombolytic therapy and underwent thrombectomy and thrombolysis. Anticoagulant therapy with bemiparin sodium (HIBOR) was initiated. Due to abnormal coagulation tests, hematology consultation was requested.

Further investigations showed normal lupus anticoagulant levels (1.16). Factor assays revealed a Factor V level of <6% (normal: 70-120%), while other factor levels were within normal limits. Anticardiolipin IgM and IgG were negative, and homocysteine was normal. APC resistance was measured at 0.64 seconds (normal: 0.91-1.19). Both Factor V Leiden and Factor II mutations were homozygous normal. Antithrombin III activity, as well as Protein C and S levels, were normal. ANA and anti-dsDNA tests were negative. A repeat Factor V level confirmed it remained <6%.

The patient had no history of bleeding episodes and had not experienced bleeding complications during previous childbirths or minor surgeries.

This case highlights the rare identification of Factor V deficiency in a patient presenting with deep vein thrombosis, an uncommon association, illustrating the complexity and variable clinical manifestations of Factor V deficiency.

Factor V deficiency is a rare coagulopathy, typically characterized by a bleeding tendency, with an incidence of approximately 1:1,000,000 in the general population. The disease is inherited in an autosomal recessive manner and is caused by various mutations in the FV gene. As FV plays a critical role in both procoagulant and anticoagulant pathways, its deficiency usually manifests with symptoms such as mucosal bleeding, postoperative hemorrhage, and menorrhagia. However, paradoxically, some patients with FV deficiency have been reported to develop thrombotic events.

In this patient, who presented with complaints of deep vein thrombosis, the absence of a bleeding history and lack of hemorrhagic complications during past surgical procedures highlights the heterogeneous clinical presentation of FV deficiency. This supports the hypothesis that FV deficiency, due to its dual roles, may predispose not only to bleeding but also to thrombosis.

Although the relationship between FV deficiency and thrombosis has not been fully elucidated, some potential mechanisms have been suggested. First, reduced TFPIα levels in patients with FV deficiency may disrupt the hemostatic balance, increasing the risk of thrombosis. Additionally, APC resistance observed in these patients could explain the hypercoagulability associated with FV deficiency.

This case is significant in that it highlights the diagnosis of a rare Factor V deficiency in a patient presenting with deep vein thrombosis. While FV deficiency is typically characterized by a bleeding tendency, the predominance of a thrombotic complication in this case underscores the heterogeneous clinical course of this disorder and the challenges in its management. Although the development of thrombosis in patients with FV deficiency is rare, such cases emphasize the complexity of hemostatic balance and the necessity for individualized treatment approaches. Further case reports and a better understanding of the underlying mechanisms may lead to the development of more effective strategies for managing patients with FV deficiency.