Anaphylaxis after Hymenoptera sting without detectable specific IgE.

Current guidelines for venom immunotherapy suggest that immunotherapy should be performed only in patients with IgE mediated systemic reactions. However, opinions on the diagnosis and treatment of patients with systemic reactions in the absence of IgE are quite varied. We present a patient with a history of atypical systemic reactions after a bee sting. Skin tests and specific IgE for bee venom were negative. We performed a sting provocation test in order to characterize the nature and mechanism of reaction. The provocation test was positive and mast cell activation was proved by tryptase elevation. We decided to treat the patient with immunotherapy. After beginning immunotherapy we were able to detect specific IgE for bee venom in the serum.