Published online: March 3, 2020
Over the last decade, a novel form of food allergy, the galactose-α-1,3-galactose (α-Gal) syndrome (AGS), has been recognized worldwide. AGS patients experience delayed severe allergic reactions after mammalian meat consumption due to IgE antibodies directed against the carbohydrate α-Gal present in mammalian meat and mammalian products. Some α-Gal containing pharmaceuticals (cetuximab, anti-venom, gelatin containing vaccines) can also induce an allergic reaction in these patients. The onset of the disease is strongly associated with tick bites. α-Gal-carrying proteins have been detected in tick saliva and AGS is actually thought to be the first allergy where sensitization is induced by allergen exposure via tick bites. As with any novel disease, it is important to gain a good understanding of the clinical and immunological features of AGS. However, until now the literature on characteristics of large AGS patient cohorts is scarce.
In a study recently published in The Journal of Allergy and Clinical Immunology: In Practice, Kiewiet and colleagues characterized a cohort of 128 patients with AGS from Sweden, both on a clinical and serological level. Medical examination and diagnosis were made by an allergist experienced in AGS. Patients filled in questionnaires regarding onset of symptoms, tick exposure, and airborne allergies. The authors also measured serum IgE reactivity against multiple food allergens, airborne allergens and tick (Ixodus ricinus) protein extract using the ImmunoCAP System.
The authors found that the majority of patients were middle-aged, with equal gender distribution. Most patients reported symptoms more than 2 hours after meat consumption, confirming the delayed nature of the reaction. Urticaria (90%) and gastrointestinal symptoms (74%) were the most common symptoms. Almost half of the patients suffered from anaphylaxis with respiratory or cardiovascular symptoms (47%), which reflects the severity of the disease. Cardiovascular symptoms were the type of symptoms most often observed in anaphylactic patients, which is atypical for food allergy. Moreover, nearly all patients belonged to the B negative blood groups, due to the structural similarities between α-Gal and the blood group B-antigen. The authors also reported that nearly all patients had been tick bitten and 75% had IgE against I. ricinus. Finally, they noted that more than half of the patients with AGS were atopic, and that atopy increased the risk of anaphylaxis with respiratory manifestations 3-fold compared to non-atopic patients. With this detailed patient characterization, the authors aim to increase the awareness of the clinical phenotypes of AGS, and thereby contribute to improved diagnosis and management of AGS patients.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.