Glynn D, Halma J, Welch H, Shakhnovich V, Friesen C
The Journal of pediatrics •
We report 3 pediatric patients who presented with only nonanaphylactic symptoms of alpha-gal syndrome. This report highlights the necessity of not discounting alpha-gal syndrome from a differential diagnosis for patients with recurrent gastrointestinal distress and emesis after consuming mammalian meat, even in the absence of an anaphylactic reaction.
The galactose-alpha-1,3-galactose (alpha-Gal) syndrome is a newly recognized and unique form of food allergy, characterized by delayed reactions to mammalian meats. This form of allergy occurs in individuals who become sensitized to alpha-Gal, a carbohydrate that is present on most mammalian tissues. Sensitization occurs after exposure to multiple arthropod bites, most commonly the lone star tick. Cases of the alpha-Gal syndrome are primarily found in the southeastern United States, which overlaps with the known geographic distribution of the lone star tick. Patients present with a history of delayed symptom onset, ~2-6 hours after ingestion of mammalian meat. As with other immunoglobulin E (IgE) mediated food allergic reactions, alpha-Gal reaction symptoms may include skin, respiratory, gastrointestinal, or cardiovascular systems, and severity may range from mild reactions to severe anaphylaxis. The diagnosis is based on the detection of alpha-Gal specific IgE (sIgE) as well as the total IgE value because some cases include patients with low total IgE levels but a high percentage of alpha-Gal sIgE to total serum IgE levels. Percutaneous testing with commercial meat skin-prick testing extracts is not a reliable tool for diagnosis. Prick-prick skin testing to fresh cooked meat may be considered, whereas intradermal testing to fresh meat is primarily reserved for research purposes. The mainstay of treatment involves avoidance of mammalian meat and medications that express the same carbohydrate antigen. With a small portion of patients, other meat-containing products should also be avoided if symptoms persist with mammalian meat avoidance alone. Prolonged avoidance of mammalian meat as well as avoidance of further tick bites can decrease alpha-Gal sIgE over time, and some patients are able to reintroduce mammalian meat into their diet.
The development of food allergies is thought to involve multiple factors, and it is unclear which conveys the most risk regarding this process. Since food allergy is a chronic disease without a cure at this time, understanding its development could provide an avenue for preventive practices and development of a curative treatment. Both historical and current data implicate maternal factors, genetics, and environmental exposures as major risk factors in the development of food allergy. An immature gut of the infant has been hypothesized as a possible route of sensitization. Breastfeeding until at least 6Â months of age has been shown to have protective factors for the newborn and may possibly improve gut permeability. Newer studies such as the LEAP and EAT investigations also looked at early exposure and prevention of food allergies; their long-term results are critical in understanding early introduction and tolerance. Cutaneous exposure, oral exposure, and food protein exposure in house dust with their relation to the food allergy course are also a path of interest. Current research has shown sensitization can occur through impaired skin such as those with eczema and a filaggrin mutation. Tropomyosin and alpha-gal also are related to the complicated immunomodulatory factors involved in food allergy and allergic response. Cross-reactivity with plant allergens, sensitization to house dust mite and cockroach, and lone star tick bites can also induce food allergens in children and adults. Together, these factors provide a cohesive beginning to understanding how food allergies can occur and can influence further investigation into prevention, treatment, and eventual cure of food allergies.
