Methods:We characterized the clinical features of a 10 year old boy with a history of walnut allergy who developed FDEIA due to tofu (a soybean product). The patient developed anaphylaxis while running during his physical exercise class after eating tofu. He presented with symptoms of cough, nasal obstruction, generalized urticaria, loss of activity and cyanosis. His symptoms improved an hour after treatment with loratadine but he was not administered epinephrine. In order to detect the causative allergenic food and other cofactors that induced the symptoms of FDEIA, we performed specific IgE test, skin prick test and ISAC. Immunoblot analysis for soybeans and soybean products using the patient's serum was also performed. Provocation tests with ingestion of tofu followed by exercise is also scheduled to be done to further confirm the diagnosis.
Results: Skin prick test with raw soybean product (tofu, fried tofu and soy milk) was strongly positive. The level of serum specific IgE to soybean was 11.90 UA/ml. The ISAC(Phadia, Uppsala, Sweden) results revealed Gly m 4, Gly m 5, and Gly m 6 as 3.3, 0.3, and 7.1 ISU, respectively. About a year and a half later, the specific IgE to soybean, Gly m 4, Gly m 5, Gly m 6 were 40.2, 3.61, 21.4, 51.7 UA/ml, respectively. The patient is well tolerant to soybean products in the absence of any exercise following the intake of the soybean products. Immunoblot analysis of soy powder with patient’s serum showed positive band between 50 and 70 kilo daltons, indicating the presence of specific IgE against storage proteins Gly m 5 and Gly m 6.
Conclusions: These results suggest the strong possibility of storage proteins such as Gly m 5 and Gly m 6 as the causative allergen of FDEIA induced by soybean (tofu).