D1.526 - Epidemiologic Characteristics of Hymenoptera Venom Allergic Patients from Two Different Environmental Areas

Italy, a long boot-shaped peninsula in Southern Europe, extends over 1.291 km. It shows marked geographical and socio-environmental differences between North (NI) and South Italy (SI). NI is predominantly urban, whereas SI is mainly rural. These differences provide a unique opportunity to compare demographic, occupational and sensitization patterns in patients with Hymenoptera venom allergy (HVA) within the same Mediterranean country, an area with a high prevalence of HVA.

We conducted a comparative observational study including 121 patients diagnosed with HVA after systemic reactions to Hymenoptera stings: 65 from the Allergy Centre of IRCCS Ca’Granda Ospedale Maggiore Policlinico, Milan (NI), and 56 from the Allergy and Clinical Immunology Unit of the G.Martino Hospital, Messina (SI). Demographic characteristics, occupational exposure, comorbidities, serum basal tryptase (SBT) levels, and diagnostic work-upwere evaluated. Sensitization to Vespula spp., Apis, Polistes dominula, and Vespa crabro was assessed.

The population was prevalently male (70.2%), most frequently aged 45-59 years (mean 50.9+15.9), without significant age differences between NI and SI (p>0.05). Occupational exposure was more common in SI (50%) than in NI (20%), where indoor jobs prevailed. In NI, stings mainly occurred during recreational activities, whereas in SI they were largely work- or hobby-related(agriculture, gardening, building, forestry). Beekeepers were present only in SI. Overall,sensitization rates were: Vespula spp 49.6%, Apis mellifera 32.2%, Polistes dominula 11.6%, and Vespa crabro 6.6%. Sensitization patterns significantly differed between regions (χ² = 10.47; p =0.015; Cramér’s V = 0.29), with Vespula spp and Apis mellifera more frequent in SI. Elevated SBT levels (>11.4 ng/mL) was found in 5,8% of patients. Systemic Mastocytosis (SM) was reported in 7cases (2 NI, 5 SI). Common comorbidities included allergic rhinitis (41%), asthma (21%), atopic dermatitis (9%), hypertension (16%), and metabolic diseases (7%). All patients underwent venom-specific immunotherapy (VIT) achieving protection from further Hymenoptera stings.

HVA predominantly affects adult males. Geographic, climatic and occupational factors can shape clinical and sensitization profiles of HVA patients within the same country, while further studies are warranted to clarify the role of sex in influencing immune reactions to stings.VIT is confirmed as a safe personalized immunomodulatory strategy.