Allergic profile and pre-diagnostic exposure to allergen-specific immunotherapy in eosinophilic granulomatosis with polyangiitis (EGPA): a single-centre retrospective observational study.

BACKGROUND

Eosinophilic Granulomatosis with Polyangiitis (EGPA) combines asthma, eosinophilic inflammation and small- to medium-vessel vasculitis. The relationship between conventional allergic phenotypes, allergen-specific immunotherapy (AIT) and subsequent EGPA remains uncertain.

OBJECTIVE

To describe specialist-adjudicated allergic manifestations in a selected EGPA cohort and explore whether pre-diagnostic AIT exposure was associated with age at EGPA onset or clinical phenotype.

METHODS

We retrospectively analysed 53 patients with expert-diagnosed EGPA, complete historical records and an allergy evaluation adequate to classify aeroallergen sensitisation, respiratory allergy, food allergy and drug hypersensitivity. Continuous variables were assessed for normality and compared using Mann-Whitney U tests; categorical variables were compared using Fisher exact tests. Analyses were exploratory.

RESULTS

Twenty-five patients (47.2%) had at least one recorded allergic manifestation. Aeroallergen sensitisation was present in 14/53 (26.4%), food allergy in 4/53 (7.5%), drug hypersensitivity in 13/53 (24.5%) and another specialist-adjudicated allergic manifestation in 1/53 (1.9%); categories overlapped. Thirteen of 14 aeroallergen-sensitized patients had multiple sensitisations. Thirteen patients were considered eligible for AIT and 7 received AIT before EGPA diagnosis. The median interval from AIT initiation to EGPA diagnosis was 13.1 years (interquartile range 5.5-20.0). No AIT-related adverse reaction was documented in available records. Exploratory comparisons did not identify statistically significant differences between allergic and non-allergic patients or between AIT-treated and AIT-eligible untreated patients.

CONCLUSION

In this selected single-centre cohort, allergic manifestations were frequent, but the inclusion process precludes population-level prevalence estimates. No association between pre-diagnostic AIT exposure and age at EGPA onset or exploratory phenotype measures was observed. No signals of potentially AIT-triggered cases were found. However, the very small AIT subgroup, retrospective design and non-systematic safety ascertainment do not exclude clinically relevant effects and do not establish causality or AIT safety. Key Points • Allergic manifestations, particularly aeroallergen sensitisation and drug hypersensitivity, were frequent in this selected single-centre EGPA cohort. • Allergic status was not associated with a clearly distinct EGPA phenotype, although subgroup comparisons were exploratory and limited by the small sample size. • No association was observed between previous allergen-specific immunotherapy and the age or clinical pattern of EGPA onset.