With interest we read the article by Krumbholz et al1 in the September 2007 issue of the Archives. Natalizumab (Biogen Idec, Cambridge, Massachusetts) is a humanized monoclonal antibody against α4 integrins, recently approved by health authorities for treating relapsing forms of multiple sclerosis.2 Infusion-related allergic reactions after the intravenous application of this drug include classical type I allergic anaphylactoid hypersensitivity reactions, typically occurring within 2 hours after infusion. The incidence of these reactions in clinical trials has been reported to be 4%.3 Krumbholz et al1 recently described a patient developing a type III hypersensitivity reaction after the second infusion of natalizumab. The clinical course of this allergic reaction appeared somewhat protracted, developing during several days; however, the overall clinical picture and the association with antinatalizumab antibodies supported the view of a delayed allergic reaction to the drug.
Leussink VI, Lehmann HC, Hartung H, Gold R, Kieseier BC. Type III Systemic Allergic Reaction to Natalizumab. Arch Neurol. 2008;65(6):849-852. doi:10.1001/archneur.65.6.851-b