000902 - Anaphylaxis Following Hymenoptera Sting in the Presence of Elevated Baseline Tryptasemia

Hymenoptera venom allergy is the leading cause of anaphylaxis in adults. Its prevalence ranges from 0.3% to 8.9% in the general adult population, compared with 20–30% in adults with mast cell disorders.

This study aims to describe the epidemiological, clinical, and paraclinical features, as well as tolerance to allergen immunotherapy, in patients with Hymenoptera venom–induced anaphylaxis and elevated baseline tryptase levels. This retrospective descriptive study was conducted in the Allergy Unit of Gabriel-Montpied University Hospital, Clermont-Ferrand, between 2015 and 2025.

Our study population consisted of 13 patients with baseline tryptase >8 µg/L and Hymenoptera venom–induced anaphylaxis, out of approximately 600 patients with Hymenoptera venom allergy. The mean age was 54 ± 14.7 years, with a male predominance. Bee stings were the most common cause. Patients often had difficulty identifying the type of wasp, and sometimes even the stinging insect itself. Severe anaphylactic reactions were most frequently associated with bee stings. In our study, nearly 75% of reactions were classified as Mueller grade 3 or 4 (Figure 1). Physical exertion was associated with the occurrence of severe reactions and was identified as the main aggravating factor. The mean baseline tryptase level was 17.24 ± 7.7 µg/L across the study population. Regarding immunotherapy, all patients reached the maintenance dose of 200 µg, indicating overall good tolerance. Anaphylactic reactions occurred in 4 patients (1 cutaneous mastocytosis, 1 indolent systemic mastocytosis), requiring enhanced premedication (3 with omalizumab and 1 with triple therapy) to reach the maintenance dose (Table 1). Unfortunately, screening for hereditary alpha-tryptasemia (HαT) and other mast cell disorders was performed in only 6 patients (2 indolent systemic mastocytosis, 1 cutaneous mastocytosis, 2 HαT, and 1 pending evaluation).

Hymenoptera venom allergy remains poorly studied regarding its specific features in patients with mast cell disorders and requires a rigorous diagnostic and therapeutic approach.