Immune tolerance in children with factors VIII and IX inhibitors: a single centre experience.

Alloimmune FVIII and FIX inhibitors are the most serious complication of haemophilia in the postviral contamination era and their optimal management remains controversial. We present 15 boys with severe haemophilia (14 with haemophilia A and 1 with haemophilia B) who have received immune tolerance at our centre over a 9-year period. Twelve of them (80%) were successfully tolerized with varying dose intensities, but three of them (including the boy with haemophilia B) failed tolerization. The factors, which were associated with successful tolerance in our group, were a low maximum inhibitor titre and a short interval between diagnosis of the inhibitor and the start of immune tolerance. The time taken to achieve immune tolerance varied from 1 to 27 months and none of the inhibitors have recurred. Two of the three boys who failed immune tolerance had had their inhibitor for 72 and 69 months, respectively before tolerance was attempted.