Spontaneously acquired factor VIII inhibitor in a 7-year-old girl.

The youngest case with spontaneously acquired inhibitor to factor VIII is reported. A 7-year-old girl without any previous disorders presented with a hemarthrosis in the left knee and developed a rapidly expanding hematoma on the right arm, shoulder and chest after an initial infusion of factor VIII concentrate (1,000 units). Circulating antifactor VIII antibody was detected. Her coagulopathy was successfully managed with an additional massive infusion of factor VIII concentrate (7,500 units) and combination therapy of prednisolone and cyclophosphamide.