Use of omalizumab for management of idiopathic anaphylaxis: A systematic review and retrospective case series.

Abstract Background Patients with idiopathic anaphylaxis (IA) may fail to respond to a combination of high-dose H1 and H2 antihistamines and mast cell stabilizers. Treatment options for these patients are currently limited. Objective To describe the clinical experience of omalizumab use for the treatment of patients with IA with no evidence of underlying clonal mast cell disorders. Methods We performed a retrospective review at 2 separate institutions of medical records of patients with a diagnosis of IA without evidence of mast cell clonality who had received treatment with omalizumab. We searched PubMed for studies describing omalizumab use in similar patients. Information on symptoms and omalizumab therapy was compiled, and response pattern of anaphylaxis was determined. Results A total of 35 patients with IA and no evidence of mast cell clonality who received omalizumab were identified. The median age was 36 years at the start of omalizumab (range, 11-54 years; n = 29). The frequency of anaphylaxis episodes before omalizumab treatment varied from 2 total episodes to several episodes per month. The most often used initial omalizumab dose was 300 mg every 4 weeks (n = 16). Most patients ultimately achieved clinical response after starting omalizumab: complete response (63%, n = 22), partial response (28.5%, n = 10), with 3 nonresponders. Conclusion Omalizumab may be an effective treatment option for patients with IA who do not have evidence of mast cell clonality and fail to respond to antihistamines and mast cell stabilizers.