Case of oral mite anaphylaxis: Contamination of wheat flour by mites determined by enzyme-linked immunosorbent assay

概要

Oral mite anaphylaxis (OMA) induces severe allergic reactions after the intake of mite- contaminated wheat flour.1,2,3,4 This is the first case of OMA diagnosed using a basophil activation test (BAT) and enzyme-linked immunosorbent assay (ELISA).

A 37-year-old woman with a history of allergic rhinitis experienced anaphylactic symptoms including rash, nausea, diarrhea, and nasal obstruction 30 minutes after the ingestion of home- made okonomiyaki cooked with mixed wheat flour stored in a plastic container at ambient temperature after opening (home flour mix). The other ingredients in okonomiyaki were pork, cabbage, and eggs and she had consumed these individual ingredients without symptoms. Furthermore, she had eaten other wheat products and okonomiyaki cooked in restaurants without symptoms.

Laboratory examination showed total IgE was 490 IU/ml and mite specific IgE (Dermatophagoides pteronyssinus: 71.0 IU/ml, and Dermatophagoides farinae: 79.9 IU/ml) in serum, but negative for wheat, gluten, omega-5 gliadin, egg yolk/white, and pork were noted. We performed skin prick tests (SPTs) using reagents supplied by Torii Pharmaceutical Co., Ltd. Natural saline was used for negative controls and histamine dihydrochloride (10 mg/ml) for positive controls. Wheal diameters were 9 mm for histamine, 19 mm for mite allergen extract, and negative for other factors (wheat and egg yolk/white). Wheal diameters were 3 mm for the home flour mix suspension and 0 mm for an unopened flour mix (Figure 1a, b, c). However, microscopic examination of the home flour mix indicated only one obscure structure and no presence of mites.

Therefore, we performed BAT using the home flour mix, the unopened flour mix, and mite allergen extract. High CD203c/CD63 expression, indicating basophil activation, was observed with mite allergen extract and the home flour mix, but not with the unopened flour mix (Figure 1d, e). The mite allergens in flours were measured by ELISA (Nichinichi Pharmaceutical Co., Ltd.). In the home flour mix, the Der f 1 and Der Gr 2 (consist of Der p 2 and Der f 2) concentrations were 16.35 ng/g and 25.22 ng/g, respectively, but were absent in the unopened flour mix (Figure 1f).

To diagnose OMA, it is suggested to i) detect mite-specific IgE; ii) perform SPTs with suspected and uncontaminated flour; iii) microscopically identify mites in the suspected flour; and iv) perform immunoassays to detect mite allergens in the suspected flour.1 An oral challenge test with mite-contaminated food is not likely to practical or not recommended and may lead to severe reactions.2,5 Kamizono et al. reported a case of OMA diagnosed by a combination of microscopic examination and BAT.2 However, in our case, ELISA, but not microscopic examination, successfully identified contamination by mites. In addition, the activated basophils were only confirmed by BAT with the mite allergen extract and the home flour mix. Therefore, 6 BAT and ELISA with suspected flour might aid the diagnosis of OMA, when microscopic examination of the suspected flour does not reveal the contamination of mites

この論文で使われている画像