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RATIONALE: In Europe, hypersensitivity reactions to ants are exceptional. In 2013 we described the first case of anaphylaxis due to Messor barbarus (MB) ant in a patient with hymenoptera venom allergy and systemic mastocytosis (SM). SDS-PAGE Immunoblotting identified an IgE binding band of 45-55 kDa in the extract of MB's body which showed partial cross-reactivity with venom protein from Apis, Polistes and especially Vespula. Thus, we decided to investigate the possible sensitization to MB proteins in a sample of patients with Hymenoptera venom hypersensitivity. METHODS: Twenty-two patients were studied. Exhaustive anamnesis of exposition and reaction to ant bites, prick test with MB's body extract (10 mg/ml), tryptase serum determination, and REMA score (Spanish Network on Mastocytosis) to predict systemic mastocytosis were carried out. RESULTS: Three women and 19 men, average age of 50 years, were studied. Sixteen presented with systemic reactions and 6 local ones. Four of 22 patients referred ant bites but only one experienced symptoms (anaphylaxis). Prick tests with MB's body extract were positive in 10 patients. Only in 3 patients, subsequently diagnosed of systemic mastocytosis, tryptase serum was positive and REMA score was more than 2 points. CONCLUSIONS: We detected sensitizations to MB ant body in almost half of patients with Hymenoptera venom hypersensitivity. Nevertheless, we do not know its clinical relevance because most of them had not suffered ant bites. But taking into account our previously reported case, we consider that the investigation of sensitization to other kinds of Hymenoptera may be of interest, especially in patients with systemic mastocytosis.

The Optilite assay allows the automated and precise quantification of C1-INH concentrations in patient samples. It could therefore be used as a tool to aid the investigation of patients with angioedema.

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