[Transient inhibitors developed in two cases of hemophilia A]

This report describes the transient development of inhibitors in two cases of hemophilia A. Case 1 was an 8-month-old boy who suffered from subcutaneous hematoma with extremely low level (1.5%) of plasma factor VIII activity (F VIII:C). He showed an inhibitor titer of 2.5 Bethesda units (BU)/ml when he suffered from measles at age 24 months with poor clinical response to factor VIII. This inhibitor elevated to 11.6 BU/ml at 29 months, but completely disappeared at 32 months. Case 2 was a 5-month-old boy who suffered from subcutaneous hematoma with extremely low level (< 1%) of plasma F VIII:C. At 8 months his inhibitor titer peaked at 19 BU/ml but subsequently declined to 11.5 BU/ml at 12 months and completely disappeared at 14 months. A review of the literature revealed that the median (range) titer of transient inhibitor initially developed at 2 (0.5-19) BU/ml on 225 (79-448) days, immediately peaked at 3.6 (0.5-60) BU/ml and disappeared by 665 (282-1140) days, suggesting that careful monitoring of F VIII inhibitors is required in the treatment of hemophilia A.