Abstract
This case involves a 12-year-old girl who had had allergic rhinitis from around age 7. At age 10, she experienced itching of the oral cavity and pharynx when she ingested Asian pear, peach, cherry, strawberry, apple, or Japanese plum. At age 11, she was suspected of having oral allergy syndrome (OAS) and was referred to our department. As the OAS was mild and temporary, we administered second-generation antihistamines and put under observation. At age 12, similar symptoms appeared when she ingested heated soy food. She was thus admitted for a more detailed examination. We performed CAP system fluorescent enzyme immunoassay (CAP-FEIA) and the oral food challenge (OFC) test. We detected the birch pollen, peach, apple, and strawberry specific IgE antibody in the CAP-FEIA test, however we did not detect the soy-specific IgE antibody. The OFC test showed positive reaction for unheated tofu (bean-curd) and soymilk. Because of poor objective findings, except mild pharyngeal itching, we could not definitely diagnose the condition. Therefore, we performed component-resolved diagnostics (CRD) to analyze allergen components. Positive results were obtained only with Bet v1 (birch pollen), Pru p1 (peach), and Gly m4 (soy); these are homologous to pathogenesis-related protein 10 (PR 10), which is a member of a family of protective proteins present in plants. We diagnosed the condition as pollen-food allergy syndrome due to cross reactivity between birch pollen and soy. The results of CRD and not the conventional allergy tests aided definitive diagnosis of this case.
