Rituximab Hypersensitivity: Evaluation, Desensitization, and Potential Mechanisms

Rituximab (Rituxan) hypersensitivity (RITS) can be severe and limits the ability to further administer the treatment. Understanding its pattern and desensitization may permit administration in difficult cases.Analyze RITS patient characteristics, hypersensitivity pattern, and desensitization outcomes to optimize management.Twenty-five patients with RITS were referred to the Allergy/Immunology Unit at Massachusetts General Hospital over 5 1/2 years. Their clinical reaction patterns were analyzed. Drug desensitizations were performed using 3 related continuous intravenous protocols that were chosen on the basis of clinical history, skin test reactivity, and the patient's previous desensitization outcomes.Of the 25 referred patients, 23 had lymphoma of various types. The 25 patients underwent 170 continuous intravenous desensitizations based on 3 related protocols, with most based on the intermediate protocol. All but 2 desensitizations were completed successfully. Overall 24% of the desensitizations were complicated by hypersensitivity reactions. Two patients with serum sickness and a patient with mast cell disorder were also successfully managed. The average hypersensitivity reaction grade was 3.0 (2-4) before desensitization and 0.41 with desensitization. Skin tests were performed in 18 patients, with 5 patients positive initially and 2 more converted from negative to positive. Skin test status was not helpful for risk stratification for hypersensitivity reactions. Tryptase level was elevated during 21% of desensitizations with reactions but rare among asymptomatic desensitizations.Nearly all patients with severe sensitivity to rituximab can be successfully desensitized. IgE-mediated mechanism and mast cell degranulation, in addition to cytokine release syndrome and tumor lysis syndrome, may contribute to a significant portion of hypersensitivity reactions among patients with RITS.