Antibodies against factor VIII occur in about 15-35% of hemophilia A patients and induce refractoriness to factor VIII substitution. In most cases, these antibodies are of the IgG class. Strategies to avoid or to treat such inhibitors are controversial. In very rare cases, factor VIII inhibitors also develop in nonhemophilic patients. Although there are anecdotal reports that these antibodies may disappear spontaneously without occurrence of bleeding tendencies, in the majority of patients the clinical course is characterized by severe hemorrhages. From 1980 to 1995, we observed ten nonhemophilic patients with acquired factor VIII inhibitors at our hospital. In most cases, a sudden bleeding tendency was observed shortly after an injury or surgery. Coagulation tests showed a prolonged aPTT and a decreased F VIII level. Other deficiencies of blood-clotting factors and acquired or hereditary von Willebrand's disease were excluded. Therapy with F VIII concentrates did not produce the expected increase. Measurement of F VIII inhibitor levels in Bethesda units/ml (BU/ml) revealed maximal values in the range of 2-128 BU/ml. Immunosuppressive therapy with azathioprine or cyclophosphamide in combination with methylprednisolone led to complete disappearance of the inhibitor, normalization of the coagulation tests, and complete remission of the bleeding tendency in seven treated patients within 6 weeks. Although the clinical course is not predictable and inhibitors may disappear spontaneously, combined therapy with methylprednisolone and azathioprine or cyclophosphamide is recommended for patients with bleeding tendency. In pregnancy, therapy should be started only with methylprednisolone; post-partum, azathioprine should be used additionally if methylprednisolone as a single drug does not lead to complete remission. In emergency situations, therapy with high doses of human factor VIII concentrate may be used. When bleeding does not cease, the additional use of activated prothrombin-complex concentrates or porcine factor VIII is indicated. Possible side effects may include hepatitis and short-lived intravascular thrombin production.

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The association of HLA-A and -B antigens with Bf alleles was investigated in 200 parents from 100 unrelated families. There were significant associations between HLA-A3 and Bf-F, B7 and Bf-S, B8 and Bf-S, B12 and Bf-F, and BW 35 and Bf-F. Three-point HLA-A,B,Bf haplotype frequencies, linkage disequilibrium parameters, and chi-square values were determined both from the genotype and from the phenotype data. Although the HLA-B,Bf associations involve antigens that are also present in the highly associated A,B and B,D haplotypes of the Caucasian population, there was--with the possible exception of HLA-A3,B7,Bf-S--no significant three-point association for HLA-A,B,Bf.

During the last ten years we observed three non-hemophilic patients with factor(F) VIII: C inhibitors (2 women aged 68 and 80 and a man aged 51). In all three cases, a sudden bleeding tendency was observed shortly after an injury or surgery. Coagulation tests showed a prolonged aPTT and a decreased F VIII: C level. Other deficiencies of blood-clotting factors and acquired or hereditary von Willebrand's disease could be excluded. Therapy with F VIII: C concentrate, cryoprecipitate, or fresh-frozen plasma did not produce the expected increase in F VIII: C. Measurement of F VIII: C inhibitor levels (Bethesda Units, BU) revealed values in the range between 9 and 64 BU. The two patients subjected to long-term therapy with a combination of prednisone (initially 2-3 mg/kg BW) and azathioprine (2-3 mg/kg BW) responded positively; the F VIII: C concentration increased. The third patient, treated only with a low dose of prednisone (30 mg/day), did not show any reaction at all. Since hereditary hemophilia A could be excluded, the inhibitors apparently were acquired. Malignant tumors did not appear. In conclusion, long-term therapy of an acquired F VIII: C inhibitor with a combination of prednisone and azathioprine may lead to complete disappearance of the inhibitor, normalization of the coagulation tests, and complete remission of the bleeding tendency.