Results in three Australian haemophilia B patients with high-responding inhibitors treated with the Malmö model.

Development of inhibitors to factor IX (F IX) is a serious complication of the treatment of patients with severe haemophilia B. Three Australian haemophilia B patients, a 22-year-old man and two 5-year-old identical twins, with high-responding inhibitors and resistant to treatment, were admitted to the centre in Malmö, Sweden, for tolerance induction according to the Malmö treatment model. This tratment consists of a combination of cyclophosphamide, F VIII of F IX, and high-dose intravenous IgG. Extracorporeal adsorption to protein A in columns, which is included in the protocol when the inhibitor titre is high at the start of treatment, had to be perforemed in the case of the twin brothers. High-purity F IX concentrates were used. The tolerance inductin was successful in the 22-year-old man and in one of the twins; they been toleant for 4 and 2 years, respectively, and are now on a home-treatment programme taking 30-40 IU F IX/kg twice weekly. These patients have no demonstrable coagulation inhibitory antibodies and in vivo reovery and half-life of infused F IX are normal. In the other twin it has not been possible to induce tolerance, though after removal of the antibodies by protein A adsorpation it is possible to achieve significant circulalting levels of F IX for 8-10 days.