Background:Recombinant factor VIIa (rFVIIa) is a highly purified recombinant protein. It is approved for the treatment and prevention of bleeding episodes associated with congenital factor VII deficiency, congenital hemophilia with inhibitors, and Glanzmann's thrombasthenia. The most commonly reported adverse events are thrombolytic in nature. In this report, we present a successful desensitization protocol administered to an infant with a history of anaphylaxis to rFVIIa. Case:A male infant with a history of gingival bleeding at the age of 6 months was diagnosed with factor VII deficiency with a factor VII level of 1%. His sister also had diagnosis of factor VII deficiency. Our patient was hospitalized at 10 months of age with generalized petechiae and bloody stools. Twenty minutes after administration of rFVIIa, he developed anaphylaxis that responded to epinephrine and supportive care. Subsequently he was evaluated at the allergy clinic, where a skin prick test with rFVIIa was negative. However, the intradermal skin test, applied with 1/1,000 (1 mu g/1 mL, 0.1 mL) dilution of rFVIIa, showed induration of 8 mm (positive reaction). Because there is no alternative treatment for factor VII deficiency, we developed a successful 13-step desensitization protocol with rFVIIa (NovoSeven(R)). Desensitization was performed an additional 2 times using the same protocol, one of which was for a head injury and the other for a swollen knee since the period between the doses was similar to 3 months. Conclusion:Allergic reactions, such as anaphylaxis can occur without prior exposure. This can be due to the high molecular weight and structural property of the biological agent. In this report, we present an effective desensitization protocol for an infant with a history of anaphylaxis to rFVIIa. Desensitization protocols in this age group should be carried out in a medical facility and with specialized staff and equipment prepared to care for anaphylaxis.