birch fruit vegetable syndrome

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Oral birch allergy syndrome:

  • patients with birch pollen allergy frequently develop hypersensitivity reactions to certain foods, e.g. apples, celery, carrots and hazelnuts

    • reactions are mainly caused by IgE-antibodies specific for the major birch pollen allergen, Bet v 1, which cross-react with homologous proteins in these foods

    • food allergy represents an important manifestation of atopic allergy
      • primary food allergy mainly affects young children whereas adults frequently develop food allergy as a consequence of an inhalant sensitization
        • pollen-related food allergy has become the most frequent form of food allergy in adolescent and adult individuals in Europe
          • a typical example is the 'birch-fruit-vegetable-syndrome'.
            • more than 70% of birch pollen-allergic individuals develop allergic reactions to stone-fruits, nuts or certain vegetables. In the majority of patients these reactions are confined to the oropharynx and summarized as 'oral allergy syndrome' (OAS)
            • nevertheless, systemic IgE-mediated reactions such as urticaria, asthma or anaphylactic shock occur occasionally

        • the major birch pollen allergen, Bet v 1, is the most relevant sensitizing protein causing this type of food allergy but minor allergens such as Bet v 2, Bet v 5 and Bet v 6 have also been shown to be involved
          • whereas these allergens are recognized by 10-32% of birch pollen-allergic patients, more than 95% display IgE against Bet v 1(4)

Notes:

  • major birch pollen allergen belongs to the pathogenesis-related (PR) protein family
    • other members of this protein family are present in various foods, such as fruits of Rosaceae (e.g. Mal d 1 in apple, Pru a 1 in cherry, Pyr c 1 in pear), vegetables of Apiaceae (e.g. Api g 1 in celery, Dau c 1 in carrot), hazelnut (Cor a 1), soybean (Gly m 4), mungbean (Vig r 1) and peanut (Ara h 8)
      • these proteins share a high degree of amino acid sequence similarity with the major birch pollen allergen resulting in a similar tertiary structure
      • thus, Bet v 1-specific IgE antibodies can bind to these dietary proteins which may cause immediate hypersensitivity reactions upon consumption of the respective foods
      • IgE-cross-reactivity between Bet v 1 and food homologues correlates roughly with the similarity of their primary protein structures

Reference:

Last reviewed 01/2018