Introduction
The incidence of anaphylaxis has continued to rise globally based on hospitalised data from Europe, United states, Australia, Brazil and some Asian countries such as South Korea and Taiwan [1, 2]. However, the actual incidence is likely to be several folds higher due to mis-diagnosis, mis-classification, due to under reporting [1] and also because allergies and anaphylaxis being neglected in many developing countries, due to other disease priorities [3]. Food allergy was shown to be the predominant cause of anaphylaxis, followed by drugs and venom, in many countries [1, 2, 4]. However, in a large proportion of cases, even after extensive evaluation, a trigger cannot be identified, and such cases are classified as ‘idiopathic anaphylaxis’[5].
Approximately 10% of children and 30 to 60% of adults presenting with anaphylaxis are classified as having idiopathic anaphylaxis (IA), as a trigger cannot be identified [5]. Mast cell disorders such as mastocytosis, mast cell activation syndrome and hereditary α-tryptasaemia, are some of the conditions that can cause IA, and screening for these diseases have been suggested in the diagnostic work-up [6]. Allergy to Galactose-α-1,3-galactose (α-gal), has shown to be important cause of anaphylaxis in those in whom a cause cannot be identified [7]. Alpha-gal allergy typically occurs 3 to 6 hours after ingestion of red meat and has shown to occur due to IgE antibodies specific to the carbohydrate epitope found on mammalian meat [8]. Since the identification of α-gal allergy as an important cause of delayed anaphylaxis, screening for the presence of allergy to α-gal has been included in the diagnostic workup in a patient, in whom a possible cause of anaphylaxis cannot be identified [7]. Other important causes where IA was shown to be food dependent exercise induced anaphylaxis (FDEIA), due to presence of IgE to omega-5-gliadin [5]. FDIEA, has indeed shown to be an important cause especially in patients who present at specialised allergy clinics. In one study, 12.2% of patients were identified as having FDIEA [9].
Although the incidence of anaphylaxis is not reported in many lower middle-income countries (LMICs), the incidence of asthma and asthma related mortality has shown to be rising [10]. Diseases related to allergies are neglected in many LMICs with adrenalin not used in many instances, in the management of anaphylaxis and long-term management of patients with anaphylaxis being sub-optimum due to the non-availability of adrenalin autoinjectors [3, 11]. Although there is no data on the incidence of anaphylaxis and other allergic diseases in Sri Lanka, there is a high prevalence of asthma and allergen sensitization reported among Sri Lankan children [11, 12]. Furthermore, many patients with anaphylaxis present to specialised allergy clinics in Sri Lanka where food allergy, FDIEA and allergy to vaccines have been identified as the predominant causes of anaphylaxis [9, 13, 14]. As food consumption patterns, genetic background, and environmental factors can lead to differences in allergen sensitization patterns in different geographical regions, we sought to identify the possible triggers of IA in Sri Lankan patients presenting to specialised allergy clinics in Sri Lanka.