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Dear Editor, Pancake syndrome is oral mite anaphylaxis caused by eating food prepared with wheat flour contaminated with mites. More than 135 cases occurring in various countries located in tropical and subtropical areas have been reported.[1] The most common culprit food is a pancake, although various foods containing flour have reportedly been causative. In cases of this disease in Japan, the causative foods have been confined to okonomiyaki and takoyaki, both of which are popular in the Kansai region of Japan.[2] To our knowledge, this is the first report of pancake syndrome induced by ingestion of tempura, a well-known Japanese dish.

A 16-year-old girl suddenly felt obstruction of the throat and developed facial oedema 2 min after ingestion of shrimp tempura, and was transferred by ambulance to the emergency outpatient service of our hospital. She had mild atopic eczema but no history of anaphylaxis or allergic reaction to seafood. Her level of consciousness was slightly depressed at that time. Her systolic/diastolic blood pressures were 101/76 mmHg and her pulse rate was 100 beats per minute. Oxygen saturation was 93%. Her face was markedly swollen but no weals were observed. Laboratory tests (haemogram and blood chemistry) showed no abnormal findings. A diagnosis of anaphylaxis was made, and she received an infusion of extracellular fluid and an antihistamine with quick relief of symptoms.

After this episode she experienced three similar episodes within 1 year, but we could not identify the causative antigens for these allergic reactions. Every episode occurred 2–15 min after eating home-made tempura and was successfully treated with early medical intervention, irrespective of the severity of the anaphylactic reaction. Her serum IgE level was 644 IU mL−1. IgE against wheat, gluten, omega-5 gliadin, shrimps, crabs, mackerel and scallops was not detected. Because the episodes occurred after ingestion of home-made tempura, but not tempura served in restaurants, we suspected that the tempura batter mix flour used by the patient's mother contained the causative allergens. Skin prick tests with this flour mix suspended in water were positive, with and without heat treatment (Fig. 1), but a test with a newly bought flour mix was negative, suggesting that the flour mix from home contained heat-stable antigens for her reaction. Microscopic inspection of the flour mix from home revealed large numbers of mites (Dermatophagoides farina; Fig. 2), calculated to be 3836 mites g−1. Taken together with her high levels of serum IgE against D. farina mites (89·7 IU mL−1), we concluded that all the episodes in this patient could be attributed to allergic reaction to storage mites in the flour, and thus we diagnosed this case as tempura-induced pancake syndrome.

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Figure 1. Skin prick tests with tempura batter mix flour. The tests with the flour mix used by the patient's mother were positive, with (d) and without (c) heat treatment, but the test with a newly bought flour mix (b) was negative. Saline was used as a control (a).

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Figure 2. Dermatophagoides farina mites (left, female; middle, male; right, larva) identified in the tempura batter mix flour by microscopic inspection (original magnification ×100).

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Pancake syndrome has been suggested to comprise (i) intolerance to nonsteroidal anti-inflammatory drugs (NSAIDs); (ii) atopic diathesis; and (iii) oral anaphylaxis induced by mites.[1] Although the most severe episode in our patient was anaphylactic shock after ingestion of tempura while taking ibuprofen for menstrual pain, she did not have a history of intolerance to NSAIDs, but did have a history of atopic dermatitis. NSAIDs might exaggerate the symptoms of this disease, possibly by increasing the absorption of antigens from the digestive system, as seen in patients with food-dependent exercise-induced anaphylaxis.[3] Tempura is a Japanese dish consisting of seafood and vegetables that are battered and fried. Tempura batter, which is made from a mixture of the soft wheat tempura flour, eggs, baking powder and spices, has been reported to be susceptible to contamination by mites.[4] Therefore, storing the flour in a sealed plastic container in the refrigerator is recommended to prevent the rapid growth of mites in such conditions.[5] The present case warns that tempura may be a causative food for pancake syndrome.

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