Acquired inhibitor against factor IX in a child: successful treatment withhigh-dose immunoglobulin and dexamethasone

The occurrence of acquired inhibitor against factor IX:C is infrequent in h aemophilia B patients and is very rare in previously healthy subjects, in w hom it is often related to underlying diseases. We describe the case of a 2-year-old girl, who was referred to our hospital with haematomas,:without previous bleeding history. Prolonged APTT, normal PT and a factor IX:C level below 1% were found. An inhibitor against facto r IX:C was detected (5.5 U mL(-1)). Her father and mother showed normal fac tor IX:C levels. Treatment with high-dose immunoglobulin (400 mg kg(-1) day (-1) for 5 consecutive days by intravenous infusion) and dexamethasone (4 m g three times a day by intravenous injection for 4 consecutive days)normali zed factor IX:C levels and overcame the inhibitor. In conclusion, high-dose immunoglobulin and high-dose dexamethasone are a s uccessful and safe immunosuppressive approach for recovery from inhibitor o ccurrence.