Acquired inhibitors of factor V

Area of Science:

• Hematology
• Immunology
• Clinical Pathology

Background:

• Acquired inhibitors to coagulation factor V (FV) are uncommon autoimmune conditions.
• These inhibitors can lead to significant bleeding complications, ranging in severity.
• Understanding the characteristics and diagnostic markers of FV inhibitors is crucial for patient management.

Purpose of the Study:

• To review clinical and laboratory data of patients with acquired factor V inhibitors.
• To identify diagnostic criteria and characterize the nature of these inhibitors.
• To explore potential associations with underlying conditions or triggers.

Main Methods:

• Retrospective review of clinical and laboratory findings in 12 patients with acquired FV inhibitors.
• Analysis of coagulation tests, including partial thromboplastin time (PTT) and Quick prothrombin time (PT).
• Assessment of inhibitor properties (e.g., immunoglobulin class) and response to normal plasma.
• Comparison with plasma from patients with hereditary factor V deficiency.

Main Results:

• Bleeding severity varied from none to severe among the 12 patients.
• Inhibitors were transient in most cases.
• A combination of prolonged PTT and PT, uncorrected by normal plasma, with normal thrombin and prothrombin times, was pathognomonic.
• Inhibitors exhibited immunoglobulin properties, including polyclonal IgG or IgM/IgG mixtures.
• A link to major surgery was suggested, though etiology remains unknown.
• No factor V antibody-neutralizing material was found in patients with hereditary FV deficiency.

Conclusions:

• Acquired factor V inhibitors present with variable bleeding and are often transient.
• Specific coagulation test patterns are indicative of FV inhibitors.
• These inhibitors are immunoglobulin-based, and their development may be associated with major surgery.