What question did this study set out to answer?

This case report examines a novel adverse drug reaction associated with Omalizumab therapy in a patient with asthma.

May 20, 2026

C32-12 A Unique Case of Breast Enlargement Linked to Anti- IgE Monoclonal Antibody Therapy

EAE A Rodriguez AraqueBolivarian University of Venezuela AHA HaleyJacksonville University BDB C DincerJacksonville University

Key Points

This case report examines a novel adverse drug reaction associated with Omalizumab therapy in a patient with asthma.
Described a case of a 49-year-old male with severe persistent asthma undergoing Omalizumab treatment every 14 days.
Monitored IgE levels and eosinophil counts before and during treatment, documenting the development and resolution of a breast mass.
Conducted a thorough workup to exclude alternative causes before linking the condition to anti-IgE therapy.
The patient developed a tender breast mass two weeks after starting Omalizumab, which grew after subsequent injections.
Lab tests remained normal, excluding other possible causes, leading to a conclusion of Omalizumab-related breast enlargement.
The breast mass resolved completely within eight weeks after discontinuation of the medication.

Abstract

Abstract Introduction Anti-IgE therapy is a cornerstone in the management of chronic inflammatory conditions. Omalizumab (Xolair), a competitive inhibitor of immunoglobulin E (IgE), blocks mast cell activation and release of inflammatory proteins and is indicated for moderate to severe persistent asthma, chronic spontaneous urticaria, and other IgE-mediated disorders. Reported adverse drug reactions (ADRs) include injection-site reactions, hypersensitivity (including anaphylaxis), and upper respiratory infections. Description of Case We describe a unique case of a breast mass in a patient with severe persistent asthma treated with Omalizumab. A 49-year-old male with asthma, former smoking history, treated hepatitis C, and cirrhosis was receiving subcutaneous Omalizumab injections every 14 days. Six months prior to presentation, laboratory testing revealed an IgE level of 468 and eosinophil count of 320, supporting biologic initiation. Two weeks after initiating Omalizumab, and following two injections into the lower abdomen, the patient observed an enlarging, tender breast mass. This mass continued to grow after a third injection, prompting an emergency department evaluation.At presentation, complete blood count, metabolic panel, and liver function tests were within normal limits. Further workup excluded alternative etiologies, implicating the anti-IgE monoclonal antibody. The patient was offered a biopsy but elected to discontinue Omalizumab. The mass resolved completely within eight weeks of cessation. His asthma therapy was transitioned to Dupilumab (Dupixent), with return to his baseline respiratory function. Discussion While anti-IgE biologics remain a cornerstone in the treatment of chronic allergic and inflammatory disease, recognition of novel adverse effects is critical. To our knowledge, this is the first reported case of Omalizumab-associated breast enlargement. This case underscores the importance of vigilance for atypical ADRs in patients receiving biologic therapies. This abstract is funded by: None

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Cite This Study

Araque et al. (Fri,) studied this question.

synapsesocial.com/papers/6a0d5025f03e14405aa9bbd3 https://doi.org/https://doi.org/10.1093/ajrccm/aamag162.559

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