Hemophilia is a bleeding disorder where blood does not clot properly, leading to prolonged bleeding after injury or surgery. Acquired hemophilia (AH) is a rare form of this condition, differing from inherited types. Unlike genetic forms present from birth, AH develops spontaneously later in life in individuals with no prior bleeding history. This condition arises due to an unexpected immune response.
What is Acquired Hemophilia?
Acquired hemophilia is an autoimmune disorder where the body’s immune system mistakenly produces proteins called autoantibodies, also known as inhibitors. These inhibitors specifically target and neutralize one of the body’s own clotting factors, most frequently Factor VIII (FVIII). The presence of these inhibitors prevents FVIII from performing its normal function in the coagulation cascade, a series of steps that leads to blood clot formation.
This condition is distinct from inherited hemophilia, which are genetic disorders. Its onset is spontaneous and non-hereditary, developing in individuals without a pre-existing genetic predisposition. The autoantibodies bind to and inactivate Factor VIII, effectively reducing its functional level in the blood. This disruption impairs the body’s ability to stop bleeding.
Understanding the Causes and Risk Factors
The development of acquired hemophilia is associated with various underlying medical conditions and physiological states. These include autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus, and Sjögren’s syndrome. Certain cancers, such as solid tumors and lymphoproliferative disorders (e.g., lymphoma and chronic lymphocytic leukemia), are also risk factors.
Pregnancy, especially the postpartum period, is another recognized association, with cases often emerging within months after childbirth. Specific medications, including certain antibiotics and interferon, have also been implicated. Infections can occasionally precede this autoimmune response. Despite these associations, about 50% of acquired hemophilia cases are idiopathic, meaning no clear underlying cause is identified.
Identifying Symptoms and Diagnosis
Individuals with acquired hemophilia often experience sudden, severe, and spontaneous bleeding episodes. Common manifestations include extensive skin bruising (ecchymoses) and muscle hematomas, which are collections of blood within muscles causing pain and swelling. Prolonged bleeding after minor injuries, surgical procedures, or childbirth is also a symptom.
Diagnosis begins with initial blood screening tests. An activated partial thromboplastin time (aPTT) test will show a prolonged result, indicating an issue within the intrinsic pathway of coagulation. To confirm the diagnosis and identify the specific inhibitor, specialized tests are performed. A Factor VIII activity assay measures the functional level of Factor VIII, and a Bethesda assay quantifies the concentration of the Factor VIII inhibitor.
Management and Treatment Options
Treatment for acquired hemophilia focuses on two primary goals: controlling acute bleeding episodes and eradicating the autoantibodies. For acute bleeding, bypassing agents are administered to promote clot formation independently of the inhibited Factor VIII. These agents include recombinant activated Factor VIIa (rFVIIa) and Factor Eight Inhibitor Bypass Activity (FEIBA).
Eradicating autoantibodies involves immunosuppressive therapy, which aims to suppress the immune system’s production of these inhibitors. Common immunosuppressive medications include corticosteroids (e.g., prednisone) and cyclophosphamide. Rituximab, a monoclonal antibody, also targets B-cells, which produce antibodies. The choice and duration of immunosuppressive therapy depend on the individual’s response and condition severity, requiring careful monitoring for side effects and relapse.