000766 - Clonal mast cell disorders, allergy to hymenoptera venom and venom immunotherapy – our experience

We include patients with clonal mast cell disorders and/or elevated serum basal tryptase among the risk factors for a more severe anaphylactic reaction after a Hymenoptera sting. Because of the risk of these patients, venom immunotherapy should be proposed to each such patient as the only causal treatment. 

We created a prospective study consisting of 93 patients who were treated with venom immunotherapy and data were collected from 2015 to 2023. In our study, we focused on the identification and characteristics of patients with an elevated concentration of serum basal tryptase (˃ 8 ng/ml) and patients with systemic mastocytosis. 

From whole enrolled patients, we found a persistently elevated concentration of serum basal tryptase (sBT) ˃ 8 ng/ml in 16,7 % of patients and diagnosed systemic mastocytosis in one patient. The most common manifestation of a systemic reaction after Hymenoptera sting in our patients with elevated sBT was loss of consciousness and hypotension. Treatment tolerance was roughly comparable in terms of the occurrence of adverse effects and the majority of adverse effects were in terms of local reactions. A total of 53,3 % of patients treated with venom immunotherapy with elevated concentration of sBT overcame natural re-exposure to Hymenoptera insects, while not a single patient developed a systemic allergic reaction requiring the administration of an adrenaline autoinjector.

Hymenoptera venom allergy occurrence is much more frequent, and the course is more severe in patients with elevated basal serum tryptase concentrations and/or clonal mast cell disorders. It is important for every patient with confirmed clonal mast cell disease to look anamnestically for the occurrence of an allergic reaction to insect venom and to consider venom immunotherapy as the only causal treatment.