Safety and effectiveness of immunotherapy in patients with indolent systemic mastocytosis presenting with Hymenoptera venom anaphylaxis

BackgroundAnaphylaxis after Hymenoptera sting has been described in patients with mastocytosis. Venom immunotherapy (VIT) is a safe and effective way to treat patients with Hymenoptera anaphylaxis, but few studies have addressed its usefulness in patients with systemic mastocytosis.ObjectiveTo study the effectiveness and safety of VIT in patients with systemic mastocytosis having anaphylaxis after Hymenoptera sting.MethodsA total of 21 mastocytosis patients—4 women (19%) and 17 men (81%) with a median age of 50 years (range, 29-74 years)—with Hymenoptera sting anaphylaxis who were treated with VIT and followed for a median of 52 months (range, 2-250 months) were studied.ResultsIn 18 of 21 patients—16 of them lacking skin involvement—anaphylaxis was the presenting symptom. Six patients (29%) experienced adverse reactions during VIT, 3 during initiation and 3 during maintenance. Twelve patients (57%) were restung while undergoing VIT; 9 (75%) presented local reactions and 3 (25%) systemic reactions, 1 of which required intubation. The Hymenoptera specific IgE decreased from 4.15 kU/L (range, 0.44-100 kU/L) before immunotherapy to 1.2 kU/L (range, 0.34-69.4 kU/L) after 4 years (P < .003).ConclusionVenom immunotherapy is effective to treat IgE-mediated Hymenoptera anaphylaxis in patients with mastocytosis. Its use is recommended despite a relatively high risk of adverse reactions during the build-up phase because it provides protection from anaphylaxis in around 3/4 of the patients.