Unpredicted adverse reaction to omalizumab

Area of Science:

• Immunology
• Allergy and Clinical Immunology
• Pharmacology

Background:

• Systemic mastocytosis (SM) patients with Hymenoptera venom allergy often experience severe reactions during venom immunotherapy (VIT).
• Omalizumab is investigated as an add-on therapy to improve VIT tolerability, but adverse effects can occur.
• Standard H1/H2-antihistamine prophylaxis may not be sufficient for severe reactions in SM patients.

Observation:

• A case of a systemic mastocytosis patient with Hymenoptera venom allergy is presented.
• Omalizumab was used as add-on therapy to facilitate VIT initiation after severe reactions to VIT.
• Unexpected omalizumab discontinuation occurred after successful VIT initiation, leading to subsequent VIT intolerance.

Findings:

• The patient experienced unexpected adverse effects leading to omalizumab discontinuation.
• Following omalizumab discontinuation, the patient lost VIT tolerability.
• Basophil activation test (BAT) results showed a correlation with both clinical tolerability and intolerance to VIT.

Implications:

• This case highlights potential challenges and unexpected outcomes of using omalizumab in SM patients undergoing VIT.
• The findings suggest that omalizumab discontinuation may negatively impact VIT tolerability in this specific patient population.
• Basophil activation testing may serve as a useful biomarker for monitoring VIT response and predicting intolerance in SM patients.