From a young age, a 63-year-old Japanese man had experienced difficulties with hemostasis during tooth extraction and epistaxis and swelling of bruised areas. He had previously been diagnosed with mild hemophilia (FVIII:C 8.5%) at age of 60 due to swelling of a right hip bruise and was administered FVIII concentrate for the first time. He had frequent bleeding around his shoulder joints and was given FVIII concentrates every time, but his hemostasis was poor. He was referred to our hospital because his FVIII activity decreased to<1% and a low-titer inhibitor (2.0 BU/ml) was detected. Because of a shoulder hematoma and new subcutaneous bleeding on both forearms, recombinant FVIIa was used to perform the hemostatic treatment. Following hemostasis, emicizumab was administered subcutaneously every 2 weeks at a dose of 3.0 mg/kg. Approximately 2 months after starting emicizumab, inhibitors were no longer detected, and FVIII activity increased to 8% after 9 months. We encountered a case of mild hemophilia A with an inhibitor that was first diagnosed in old age. The incidence of inhibitors in non-severe hemophilia A is about 10%, and about 70% of those resolves spontaneously. In this case, suppression of bleeding by emicizumab may have contributed to the spontaneous disappearance of the inhibitor.
Keywords: Emicizumab; Factor VIII inhibitors; Hemophilia A.