Anaphylaxis to peanut in a patient predominantly sensitized to Ara h 6.
Diagnosis of peanut allergy has improved thanks to component-resolved diagnostics. Peanut allergen component Ara h 2 is considered to indicate true peanut allergy. The component Ara h 6 is structurally similar to Ara h 2, but the diagnostic value of analyzing IgE antibodies to Ara h 6 is unclear. A boy sensitized (≥0.35 kU(A)/l) to Ara h 8 but not to Ara h 1, Ara h 2 and Ara h 3 was challenged with peanut and developed grade II anaphylaxis. In serum collected at the time of challenge a doubling of IgE to the peanut allergen extract was observed compared to allergy testing 9 months earlier. In contrast, IgE levels to Ara h 1, Ara h 2, Ara h 3 and to Ara h 8 were rather unchanged. After another 2 months, Ara h 6 was analyzed and revealed a level of 24 kU(A)/l whilst Ara h 2 was 0.12 kU(A)/l. We suggest that IgE sensitization to Ara h 6 caused the reaction and conclude that analyses of IgE levels to peanut and peanut components should be performed in connection with a challenge. Furthermore, levels to Ara h 2 below 0.35 kU(A)/l may still indicate a risk of severe reaction at the time of challenge since in rare cases, Ara h 6 IgE antibodies may be present without occurrence of IgE antibodies to Ara h 2.
National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. anna.asarnoj@ki.se
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A
Asarnoj
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Glaumann
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L
Elfström
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G
Lilja
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J
Lidholm
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Nilsson
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M
Wickman
D055516:2S Albumins, Plant / Q000009:adverse effects* / Q000276:immunology*; D000293:Adolescent; D000485:Allergens / Q000009:adverse effects* / Q000276:immunology*; D000707:Anaphylaxis / Q000209:etiology* / Q000276:immunology*; D000918:Antibody Specificity; D052179:Antigens, Plant / Q000009:adverse effects* / Q000276:immunology*; D003429:Cross Reactions; D006023:Glycoproteins / Q000009:adverse effects / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D008297:Male; D021183:Peanut Hypersensitivity / Q000150:complications* / Q000175:diagnosis / Q000276:immunology*
D055516:2S Albumins, Plant; D000485:Allergens; D052179:Antigens, Plant; C500890:Ara h 2 allergen, Arachis hypogaea; C492737:Ara h 6 allergen, Arachis hypogaea; D006023:Glycoproteins; D007073:Immunoglobulin E