Title :Shrimp-Dependent Exercise-Induced Anaphylactic Shock induced by Slight Sensitization to Arginine KinaseAuthor Name :Tomoki Yaguchi1、Fumi Ishikawa1、Chisato Jimbo1、Marei Omori1、Kouhei Hagino1、Daisuke Harama1、Kotaro Umezawa1、Daichi Suzuki1、Seiko Hirai1、Kenji Toyokuni1、Kiwako Yamamoto-Hanada1、Shuyuan Mu2、Nayu Sato2,3、Masashi Nakamura2,3,4、Akiko Yagami3,4、Tatsuki Fukuie1Name of Institution :1. Allergy Center, National Center for Child Health and Development, Tokyo, Japan.2. General Research and Development Institute, Hoyu Co., Ltd., Aichi, Japan.3. Collaborative Department of Advanced Allergy and Immunology, Fujita Health University School of Medicine, Aichi, Japan.4. Department of Allergology, Fujita Health University School of Medicine, Aichi, Japan.A running title :Shrimp-FDEIA Shock Induced by Low AK-IgECorresponding author :Tatsuki FukuieAllergy Center, National Center for Child Health and Development, Tokyo, Japan2-10-1 Ookura Setagaya-ku Tokyo JapanTel: +81-3-3416-0181E-mail address: fukuie-t@ncchd.go.jpWord Count for Main Text : 937Number of figures and tables : 1 figure and 1 tableConflict of interest :AY received research funding from Hoyu Co., Ltd. SM, NS, and MN are employees of Hoyu Co., Ltd. The remaining authors declare no conflicts of interest.Financial suppor t: NoneAbstract : NoneKeywords :Food-dependent exercise-induced anaphylaxis; Shrimp; Arginine kinase; Component-specific IgE test; Basophil activation testMain text :To the EditorFood-dependent exercise-induced anaphylaxis (FDEIA) is a condition where exercise induces anaphylaxis following the consumption of certain foods. In Japan, crustaceans are the second most prevalent causative food after wheat, with shrimp responsible for about 18% of all cases1. Exercise restriction for 2-4 hours after ingestion of the allergic food is recommended in FDEIA2. However, such restrictions can significantly affect a patient’s quality of life. Therefore, a provocative test is employed to confirm the diagnosis when the causative food cannot be identified through clinical history or allergy tests.We present a case of shrimp-induced FDEIA where slight sensitization to arginine kinase might cause anaphylactic shock, despite a negative shrimp-specific IgE test. This study was approved by the Ethics Committee of the National Center for Child Health and Development (Reference number: 2022-182). Written informed consent was obtained from the patient and his guardians.A 15-year-old boy presented with unexplained allergic symptoms occurring during exercise. Approximately 90 minutes after consuming raw Pacific white shrimp (Litopenaeus vannamei ), fried shrimp (species unknown), wheat, tuna, yellowtail, salmon, shishamo, chicken, and rice, he developed generalized erythema and wheals while playing tennis. He had previously tolerated all these foods without allergic symptoms. His medical history included bronchial asthma, atopic dermatitis, milk allergy, and allergic rhinitis.Specific IgE test (ImmunoCAPⓇ, Thermofisher Scientific, Uppsala, Sweden) was negative for shrimp, wheat, and ω5-gliadin (cutoff >0.35 UA/mL). Skin prick test was positive for L. vannamei (raw) and Penaeus indicus (heated), but negative for commercial shrimp allergen scratch extract (Torii Pharmaceutical Co., Ltd., Tokyo, Japan), northern shrimp (Pandalus borealis ), and Sakura shrimp (Sergia lucens ) (Table 1). A wheal diameter >3 mm or greater than half of the positive control was considered a positive result. Both the oral food challenge forL. vannamei and the exercise provocation test with L. vannamei were negative. Subsequently, a combined provocation test with approximately 20 g of L. vannamei and 500 mg of aspirin was conducted based on Japanese food allergy guidelines2. The shrimp dose was set based on the amount that previously elicited symptoms, referencing prior reports3,4. Anaphylactic shock was diagnosed 15 minutes after completing the treadmill exercise, characterized by widespread wheals, tachycardia, and hypotension. Due to prolonged hypotension, four intramuscular adrenaline injections (0.5 mg each), a bolus of extracellular fluid, and oxygen administration were required. Based on the provocation test results, shrimp-induced FDEIA was confirmed. The patient was advised to eliminate shrimp and crab, and he has not experienced any further symptoms since then.Basophil activation tests (BAT) (BML, Inc., Tokyo, Japan) revealed an upregulation of CD203c expression on the basophils in response toL. vannamei (raw and heated), black tiger shrimp (Penaeus monodon ) (raw), but not to P. borealis (raw) (Table 1). Two-dimensional electrophoresis and western blotting (2D-WB) usingL. vannamei extract demonstrated IgE reactivity to approximately 35 kDa protein (Figure 1B). Mass spectrometry performed with nano LC-MS/MS (eksigent ekspertTM nano LC, TripleTOF® 6600 [SCIEX]) and Protein PilotTM software 5.0 (SCIEX) (DB used: NCBI, Crustacea) identified the protein as arginine kinase (Lit v 2). Enzyme-linked immunosorbent assay (ELISA) detected specific IgE only to arginine kinase, while the remaining components were negative (Figure 1C).This case illustrates shrimp-induced FDEIA in the absence of detectable shrimp-specific IgE by ImmunoCAP®. Despite negative oral food challenge and exercise provocation test, the combination of shrimp ingestion and aspirin-induced exercise triggered severe anaphylaxis requiring multiple adrenaline injections. This underscores the need for safer and more accurate diagnostic approaches beyond provocation testing.Major shrimp allergens include tropomyosin (Lit v 1), arginine kinase (Lit v 2), myosin light chain (Lit v 3), and sarcoplasmic calcium-binding protein (Lit v 4)5. Recent study identified additional allergens such as P-75 homologue and fructose 1,6-bisphosphate aldolase(FBPA)in shrimp-induced FDEIA6. In the present case, 2D-WB, mass spectrometric analysis, and ELISA revealed case-specific IgE reactivity to arginine kinase (Lit v 2), with no reactivity to other previously reported allergen components. The negative shrimp-specific ImmunoCAP® in this case may reflect weak sensitization to arginine kinase, as confirmed by 2D-WB and ELISA. This suggests that even low-level sensitization to arginine kinase, undetectable by ImmunoCAP®, can trigger life-threatening reactions in the presence of co-factors such as aspirin or exercise, even when shrimp intake is relatively low3.In the present case, the BAT was positive for L. vannamei (both raw and heated), and P. monodon (raw), but negative for P. borealis (raw). Lit v 2 has been reported to be heat-stable and highly homologous to Pen m 2, an arginine kinase derived from P. monodon 7–9. In contrast, no arginine kinase ofP. borealis has been identified. The BAT results in the present case are consistent with these previous findings. This means that the BAT could detect a low-level sensitization to Lit v 2 in this case, highlighting its utility in the diagnosis of shrimp-induced FDEIA, similar to the diagnosis of shrimp allergy10. Moreover, a study involving 37 cases of suspected shrimp allergy demonstrated the diagnostic utility of the Lit v 2-specific IgE test in shrimp allergy. The positive ELISA result for arginine kinase in this case implies that component diagnosis, like BAT, might be helpful not only in shrimp allergy but also in shrimp-induced FDEIA5.A notable feature of this case was the development of anaphylactic shock during an exercise challenge test combined with aspirin administration, despite undetectable sensitization on ImmunoCAP®. It is essential to recognize that even minimal sensitization to the etiological allergen can precipitate severe manifestations in FDEIA when exacerbating factors are present. To avoid severe reactions during the provocation test, safer and more precise diagnostic methodologies are needed. This case highlighted the potential role of component-specific IgE test and BAT in this context.Acknowledgements : None.Key message :Even minimal sensitization to a causative allergen can induce severe symptoms in food-dependent exercise-induced anaphylaxis when cofactors are present. Component-resolved diagnostics and basophil activation tests may support the diagnosis.References :1. Morita E, Kunie K, Matsuo H. Food-dependent exercise-induced anaphylaxis. J Dermatol Sci . 2007;47(2):109-117. doi:10.1016/j.jdermsci.2007.03.0042. Ebisawa M, Ito K, Fujisawa T, et al. Japanese guidelines for food allergy 2020. Allergol Int . 2020;69(3):370-386. doi:10.1016/j.alit.2020.03.0043. Asaumi T, Yanagida N, Sato S, Shukuya A, Nishino M, Ebisawa M. Provocation tests for the diagnosis of food-dependent exercise-induced anaphylaxis. Pediatr Allergy Immunol . 2016;27(1):44-49. doi:10.1111/pai.124894. Ballmer-Weber BK, Fernandez-Rivas M, Beyer K, et al. How much is too much? 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