Prevention of Anaphylaxis Episodes in Idiopathic Anaphylaxis by Omalizumab

Introduction: In 15–35 percent of patients with anaphylaxis, the triggering allergen cannot be found; therefore, a diagnosis of idiopathic anaphylaxis (IA) is made. We report on the outcomes in patients with IA treated with omalizumab. Methods: We included consequent omalizumab-treated IA adult patients treated with omalizumab 300 mg every 4 weeks. Results: Out of 7 patients, 6 were female, median age 40 years with the frequency of anaphylaxis episodes from 3 in 2 years to 5 in 4 months. Baseline tryptase ranged from 1.71 to 12.0 μg/L. An increase in tryptase during anaphylaxis was documented in 6 patients. Activating KIT p.D816V variant was detected in 2 patients. One patient also had hereditary alpha-tryptasemia (HαT). The duration of omalizumab treatment was 0.5–7.5 years. None of the patients have experienced an anaphylactic reaction since the start of treatment. Mild systemic reactions were reported in 6 patients (86%). The presence of underlying cMCD had no impact on the treatment outcome. Conclusion: All patients in our study had complete responses to omalizumab. The presence of KIT p.D816V and HαT did not influence the response to omalizumab treatment.