Agaricus bisporus mushroom anaphylaxis: A case report and review of the literature

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Anaphylaxis in response to edible mushrooms is uncommon, and sensitization may be independent of occupational exposure. Globally, A garicus bisporus is one the most cultivated mushroom species, comprising the button, portobello, and Swiss brown varietals. Our aim was to describe a case of anaphylaxis in an older nonatopic patient following ingestion of A bisporus and undertake a review of the literature. A 77-year-old female was referred to the allergy clinic with a history of grade 3 hypotensive anaphylaxis following ingestion of a mushroom omelette. Her tryptase level 4 hours following acute symptoms was elevated. She continued to consume all other omelette ingredients with the exception of mushroom. Additional investigations included specific IgE testing as well as comprehensive skin prick testing (SPT) to raw and boiled mushrooms. One month after her index reaction, the result of SPT to boiled button mushroom was positive. The patient's baseline tryptase level was normal. The results of further SPT with other commonly available boiled mushrooms (the A bisporus mushrooms portobello and Swiss brown, as well as enoki, oyster, and shiitake mushrooms) were also positive.A review of the literature revealed 27 other cases, with an average patient age of 28.8 years (range 8-68 years) and no gender predisposition. Cases from Europe (n= 14, 51.8%) and Asia (n= 12, 44.4%) comprised the majority of the reports. A bisporus was reported in more than one-third of the cases (n= 10, 37.1%) from Australia, India, Portugal, Spain, and the United Kingdom. Cross-sensitization among the edible mushroom species was evident for those individuals who were tested, but no clear and consistent pattern was identified. In some cases, further diagnostics identified α-mannosidase, α-trehalose, mannitol, and ribosomal protein as specific mushroom allergens. Clinicians should be aware of mushroom as a cause for anaphylaxis, especially in nonatopic and de novo presentations.