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Choosing wisely: omalizumab therapy for idiopathic anaphylaxis

Published online: November 18, 2020
Idiopathic anaphylaxis (IA) is a diagnosis of exclusion and thus eliminates the option for therapy targeted at the precipitating agent. Because these reactions can be severe, it would be helpful to have a therapy that could prevent anaphylaxis while trying to identify the trigger or while the disease regresses to a convalescent state.

Carter et al designed the first randomized double-blind, placebo controlled (DBPC) study of the efficacy of omalizumab in preventing episodes of IA over six months in adult patients where anaphylaxis prior to entry was documented in an ER or doctor’s office with ≥6 episodes/yr and where a marrow biopsy ruled out an underlying clonal mast cell disorder. Nineteen patients were enrolled, and 16 patients completed the study. The outcomes were reported in the The Journal of Allergy and Clinical Immunology (JACI).

No statistically significant difference was demonstrated between the placebo and treated groups, although there was a trend for efficacy in the treatment group, particularly after 60 days. This outcome may have been in part the result of the natural history of IA to lessen in frequency and severity in some individuals over time. Overall, the safety profile was favorable without long-term side effects.

Administration of omalizumab to patients with severe recurrent IA in the absence of a clonal mast cell disorder may not uniformly prevent subsequent episodes of IA. If omalizumab is administered, careful monitoring is required to determine continuing need and evaluate success because the natural history of IA in some patients is to decrease in severity and frequency with time.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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