Alpha-gal suspected as trigger in idiopathic anaphylaxis cases
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Key takeaways:
- 47.1% of patients sensitized to alpha-gal did not have any detectable IgE for other allergens.
- 35.3% of those sensitized to alpha-gal had consumed mammalian meat before developing anaphylaxis.
Alpha-gal may have triggered idiopathic anaphylaxis in patients screened at a specialized allergy clinic, according to a letter published in Clinical and Translational Allergy.
The cohort even included patients who had not eaten any mammalian meat, Thushali Ranasinghe, MBBS, lecturer at University of Sri Jayewardenepura and clinical researcher in the university’s allergy, immunology and cell biology unit, Nugegoda, Sri Lanka, and colleagues wrote.
Between January and December 2021, 65 (42 female; 49 adults) of 200 patients with anaphylaxis screened at the clinic had idiopathic anaphylaxis, including eight (12.3%) with grade 1, 46 (70.8%) with grade 2 and 11 (16.9%) with grade 3 anaphylaxis.
Testing revealed 34 patients (14 male; 22 adults) with specific IgE to alpha gal (52.3%). Other common sensitizations included house dust mites (n = 20; 30.8%), grass pollen (n = 16; 24.6%), tree pollen (n = 9; 13.8%) and cow’s milk (n = 11; 16.9%).
Among the alpha-gal sensitizations, 16 (47.1%) had no detectable IgE for other allergens and 12 (35.3%) had consumed mammalian meat before developing anaphylaxis, leading the researchers to suspect that alpha-gal allergy was the probable cause of their anaphylaxis.
The group also included 14 who had consumed milk products and two who had consumed gelatin before their reactions. However, the researchers said, the trigger was unknown or unrelated to alpha-gal for eight of the patients.
Noting that some ethnic groups in Sri Lanka consume less mammalian meat, the researchers pointed out that 16 of the 34 patients with sensitization to alpha gal had never eaten mammalian meat.
A tick bite may have led to specific alpha-gal in these patients, the researchers suggested, but they could not determine if the presence of alpha-gal-specific antibodies was part of what triggered their anaphylaxis.
Symptoms developed between a half hour and 6 hours after eating, which the researchers said was typical for alpha-gal allergy. The patients with alpha-gal all reported anaphylaxis, with an average of two episodes, and those who did not have alpha-gal reported an average of three episodes.
The most common symptoms in both groups were urticaria and itching. The patients who did not have alpha-gal had more difficulty breathing, swelling of the lips and syncope (P < .05). The patients with alpha-gal had more diarrhea and abdominal pain, but the researchers did not consider it a significant difference.
The 11 patients who were sensitized to cow’s milk also were sensitized to alpha-gal. The researchers additionally noted that 14 of the alpha-gal patients did not eat mammalian meat before their anaphylaxis but they had consumed milk products, including three who had consumed fermented buffalo milk instead of cow’s milk.
The researchers said the anaphylaxis in these cases may have been due to sensitization to bovine-gamma-globulin, lactoferrin and lactoperoxidase in the milk, with 10 of these patients testing positive for major cow allergens.
Finally, the researchers said, the two patients with anaphylaxis after eating products that included gelatin also had specific antibodies to alpha-gal. Previous research has indicated alpha-gal in gelatin products, leading the researchers to suspect it may have been a trigger in these cases.
Although many of these cases of idiopathic anaphylaxis included sensitization to alpha-gal, which probably caused these reactions, the researchers said, additional research is needed before the significance of this sensitization could be determined.