Atopy and Idiopathic Anaphylaxis

Idiopathic anaphylaxis (IA) is a severe systemic allergic reaction where no cause is found. Prior studies have shown that IA patients may have higher rates of atopy. We investigated the association between specific atopic conditions, including asthma, allergic rhinitis, and eczema, and IA. This retrospective study identified 149 patients with ICD-10 codes of anaphylaxis or anaphylactic shock in the last 5 years via electronic medical record. Thirty-six patients were included as meeting criteria for idiopathic anaphylaxis by clinical history. Thirty-one patients had baseline tryptase levels, of which 30 were within normal limits. Means were calculated for number of episodes, baseline tryptase level, age, and eosinophil count. We calculated the percentage of men/women and of those with IA and a history of asthma, allergic rhinitis, or eczema. We also calculated the percentage of patients with IA with a history of atopy compared to those who were non-atopic. The mean age of patients was 38 (SD 15.77), and 88% of patients were women. The mean number of episodes was 3.55 (SD 3.96). The mean baseline tryptase level was 3.96 ng/mL (SD 1.92), and the mean absolute eosinophil count was 140 cells/microL (SD 130). The percentage of patients with IA with and without atopy was 69% and 30%, respectively. Of those with IA, 38% had asthma, 30% had allergic rhinitis, and 16% had eczema. The vast majority of patients with idiopathic anaphylaxis were women. Atopy was associated with idiopathic anaphylaxis, and asthma was the most commonly associated atopic condition.