[Successful treatment of traumatic intramuscular hemorrhage with coagulation factor VIII replacement in a patient with congenital hemophilia A with decreased inhibitor activity by emicizumab therapy].

The patient is a 45-year-old man who was diagnosed with severe hemophilia A during childhood and received FVIII replacement therapy, which became ineffective due to inhibitor production (5-225 BU/ml). After initiating emicizumab therapy, bleeding symptoms markedly improved, but he developed an intramuscular hematoma at the right thigh due to a fall. He was hospitalized and maintained on bed rest; however, the size of the hematoma increased, and anemia developed. Since the inhibitor level was markedly decreased at 0.6 BU/ml, a recombinant FVIII preparation was administered, and the size of the hematoma decreased along with an increase in FVIII activity. Levels of the inhibitor increased to 54.2 BU/ml, but tended to decrease during continued emicizumab treatment. Emicizumab therapy seems useful in hemophilia A patients with inhibitor production.