(P-HC-1) A Case of Acquired Factor V Deficiency with Correction of Activated Partial Thromboplastin Time and Prothrombin Time Mixing Studies

Sunday, October 20, 2024

12:00 PM - 1:00 PM

Presenting Author(s)

BA

Bayan Alquran, MD

University of Louisville, Kentucky, United States

Background/Case Studies:

Background:
Factor V deficiency is a rare type of bleeding disorder that can be either inherited or acquired, and present on a spectrum of asymptomatic with laboratory abnormalities to massive hemorrhage. Congenital factor V deficiency (CFVD) is an autosomal recessive disorder with an estimated prevalence of 1:1,000,000. Acquired factor V deficiency (AFVD) is more rare, with approximately 200 cases or case series reported. Factor V deficiency is categorized as mild, moderate, or severe based on the percentage of factor V in plasma, i.e., ( >10%, 1 to 10%, < 1%, respectively).
The acquired form may be due to inhibitors formed in association with conditions or treatments such as autoimmune diseases, antibiotics, blood transfusions, infections, etc. Approximately 20% of patients with factor V inhibitors are idiopathic with no apparent cause.

Study

Design/Methods:

Case presentation:
An 80-year-old man with a history of non-Hodgkin lymphoma and status post antibiotic treatment for bilateral thigh cellulitis, presented with hematuria and abnormal coagulation studies. His laboratory findings included a prolonged prothrombin time (PT) of 60 s (international normalized ratio (INR) of 5), and a prolonged activated partial thromboplastin time (aPTT) of 200 s, which were both corrected/nearly corrected in multiple mixing studies performed. Further testing showed a decreased factor V level of < 1% (normal 65-150%) and negative factor V inhibitor titer studies (< 0.4 BU). Other factor levels tested were within normal limits. The patient was ultimately treated with multiple units of fresh frozen plasma (FFP), pRBC, platelets, and immunosuppressants. Coagulation tests were repeated several weeks following initial presentation, and the differences observed included near normal coagulation studies: PT of 17.3 s (INR of 1.64), aPTT of 45.5 s, and a significantly increased factor V level of 32%.

Results/Findings:

Discussion:
Acquired factor V deficiencies are caused by three proposed mechanisms: spontaneous autoantibodies, antibodies cross-reacting with anti-bovine factor V, and alloantibodies. Clearance-facilitating antibodies as opposed to factor neutralizing antibodies could explain a lack of laboratory evidence for an inhibitor. Additionally, review of the literature shows that some factor V inhibitors may demonstrate prolonged time dependence in mixing study incubation.

Treatment relies on immunosuppressants and factor replacement in the form of FFP and/or platelet transfusion since no factor V concentrate is commercially available.

Conclusions:

Conclusion:
This is a presentation of an interesting case of severe acquired factor V deficiency, with no laboratory evidence of an inhibitor. While presence of an inhibitor typically results in failed correction of mixing studies, correction may not absolutely rule out the possibility of an inhibitor.