Cytotoxic suppression of acquired factor VIII:C inhibitors

Article Abstract:

Factor VIII:C inhibitors are autoantibodies that are produced by the immune system and are present in the blood. They inhibit the action of factor VIII, a protein necessary for normal blood clotting, and they cause a life-threatening bleeding disorder known as acquired hemophilia. Factor VIII:C inhibitors can develop in patients with autoimmune diseases, malignant blood disorders, or skin conditions. They can occur during pregnancy or drug therapy. Drugs that suppress the immune system have been used to treat patients with factor VIII:C inhibitors. Successful treatment is dependent upon the ability to reduce the amount of factor VIII:C inhibitor present in the blood. The most commonly used drugs for this purpose are corticosteroids (prednisone) and cyclophosphamide. Corticosteroids alone are effective in about half the patients with acquired hemophilia. Cyclophosphamide is useful for patients who do not respond to treatment with corticosteroids. Treatment with cyclophosphamide is limited to six weeks because it can suppress the bone marrow, cause infertility, and increase the risk of developing cancer. In some cases, a combination of prednisone and cyclophosphamide may be beneficial. In many cases, factor VIII:C inhibitors that develop during pregnancy disappear during the postpartum period; similarly, when the autoantibody occurs during drug therapy, the condition may resolve when the drug reaction subsides. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Drug therapy, Corticosteroids, Adrenocortical hormones, Immunosuppressive agents, Cyclophosphamide

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Acquired inhibitors in malignant and nonmalignant disease states

Article Abstract:

Factor VIII:C is a blood protein that plays an essential role in the formation of blood clots to stop bleeding. Acquired hemophilia is a potentially life-threatening bleeding disorder that develops when the immune system begins to make proteins called autoantibodies that inhibit the activity of factor VIII:C (factor VIII:C inhibitors). Factor VIII:C inhibitors can develop in patients of all ages, but the majority of cases occur in patients over 50 years. In a study of 215 nonhemophiliac patients who spontaneously developed factor VIII:C inhibitors, 46 percent of the patients had no other associated illness. However, 18 percent of the patients had autoimmune disorders (such as rheumatoid arthritis or systemic lupus erythematosus), 7 percent had malignant blood disorders (such as plasma cell dyscrasia or lymphocytic leukemia), 7 percent were postpartum women, 5 percent had skin conditions (such as psoriasis, dermatitis, or pemphigus vulgaris), 5 percent had been treated with drugs (such as penicillin, sulfa drugs, or phenytoin), and 12 percent had asthma, diabetes, hepatitis or were recipients of multiple blood transfusions. Treatment with purified porcine (pig) factor VIII:C along with cyclophosphamide and prednisone has been successful in treating some patients with this autoimmune blood disorder. (Consumer Summary produced by Reliance Medical Information, Inc.)

Hemophilia

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An introduction to factor VIII inhibitors: the detection and quantitation

Article Abstract:

Blood clotting factors are proteins that are found in the blood. They play a vital role in the formation of blood clots to stop bleeding. Factor VIII (also called antihemophilic factor) is a blood clotting factor that is deficient in individuals who have hemophilia type A. In rare cases, the immune system of nonhemophiliacs makes proteins called autoantibodies that interact with and inhibit the activity of a small portion of the factor VIII molecule called factor VIII:C. These autoantibodies are called factor VIII:C inhibitors and they develop in one of every 5 million people. They cause the same bleeding disorder that is present in the inherited form of hemophilia type A. To treat this condition, the inhibitor must be identified and quantified so that the severity and risk of bleeding can be determined. Factor VIII:C inhibitors are identified by mixing normal blood with blood from the patient and measuring the time required for the mixture to clot. The amount of inhibitor present is determined using a procedure called the Bethesda assay, which measures the inactivation of a known amount of purified factor VIII added to a sample of the patient's blood. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Blood coagulation tests

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