A case of white bean allergy.

White bean allergy is uncommon and rarely reported. Herein, we report a case of white bean allergy in a patient with Down syndrome. A 7-year-old girl with Down syndrome experienced allergic symptoms twice after eating white bean and visited our hospital for a food allergy investigation. An ImmunoCAP assay revealed a white bean-specific IgE (13.4 kU_A/L) in the patient's serum. In addition, her skin prick test result was positive. Moreover, ingestion of 2 g of boiled white beans in an oral food challenge test induced intermittent cough, desaturation, generalized urticaria, abnormal sleep, and mild hypotension. Thus, we diagnosed the patient with white bean allergy. We performed western blotting and mass spectrometric analysis and detected the following allergens: Phytohemagglutinin, group 3 late embryogenesis abundant protein, lipoxygenase, and legumin. In addition, we detected several candidate allergenic proteins for the first time. White bean, runner bean, or azuki bean was considered the primary source of sensitization because although immunoblotting inhibition tests revealed that the abovementioned beans inhibited other legumes, soybean, which she tolerates, showed little inhibition of the other legumes. However, we could not confirm whether the patient could ingest legumes other than soybean or white bean because her family did not wish to continue with further testing. This is the first report of a case of systemic allergic reactions to white bean in a child with Down syndrome. Further studies are needed to identify white bean allergens and understand the relationship between Down syndrome and white bean allergy.