RESULTS IN 3 AUSTRALIAN HEMOPHILIA-B PATIENTS WITH HIGH-RESPONDING INHIBITORS TREATED WITH THE MALMO MODEL

Development of inhibitors to factor IX (F IX) is a serious complicatio n of the treatment of patients with severe haemophilia B. Three Austra lian haemophilia B patients, a 22-year-old man and two 5-year-old iden tical twins, with high-responding inhibitors and resistant to treatmen t, were admitted to the centre in Malmo, Sweden, for tolerance inducti on according to the Malmo treatment model. This treatment consists of a combination of cyclophosphamide, F VIII or F IX, and high-dose intra venous IgG. Extracorporeal adsorption to protein A in columns, which i s included in the protocol when the inhibitor titre is high at the sta rt of treatment, had to be performed in the case of the twin brothers. High-purity F IX concentrates were used. The tolerance induction was successful in the 22-year-old man and in one of the twins; they have b een tolerant for 4 and 2 years, respectively, and are now on a home-tr eatment programme taking 30-40 IU F IX/kg twice weekly. These patients have no demonstrable coagulation inhibitory antibodies and in vivo re covery 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 adsorption it is possible to achieve signific ant circulating levels of F IX for 8-10 days.