Alpha-Gal Allergy as a Cause of Intestinal Symptoms in a Gastroenterology Community Practice. Issue 3 (March 2021) - Richards, Nathan E.
Abstract : Immunoglobulin E to galactose-α-1, 3-galactose (alpha-gal) is causal in an allergic syndrome most commonly associated with delayed reactions to mammalian meat. In North America IgE sensitization to alpha-gal is caused by bites of the Lone Star tick. There is increasing evidence that suggests that the syndrome may manifest as isolated gastrointestinal symptoms. We performed a retrospective review of 4 years of patient encounters in a community practice to evaluate the frequency of alpha-gal seroreactivity, associated gastrointestinal symptoms, and response to avoidance of mammalian food products. Abstract : Objectives: Immunoglobulin E (IgE) to galactose-α-1, 3-galactose (alpha-gal) is a recently appreciated cause of allergic reactions to mammalian meat and dairy. In eastern North America Lone Star tick bites are the dominant mode of sensitization. Classically the alpha-gal syndrome manifests with urticaria, gastrointestinal symptoms, and/or anaphylaxis, but increasingly there are reports of isolated gastrointestinal symptoms without other common allergic manifestations. The objective of this retrospective study was to determine the frequency of IgE to alpha-gal in patients presenting with unexplained gastrointestinal symptoms to a community gastroenterology practice, and to evaluate the symptom response to the removal of mammalian products from the diet in alpha-gal–positive individuals. Methods: An electronic medical record database was used to identify patients with alpha-gal IgE laboratory testing performed within the past 4 years. These charts were reviewed for alpha-gal test results, abdominal pain, diarrhea, nausea and vomiting, hives, bronchospasm, diagnosis of irritable bowel syndrome, postprandial exacerbation of symptoms, meat exacerbation of symptoms, patient recall of tick bite, other simultaneous gastrointestinal tract diagnoses, and clinical improvement with mammalian food product avoidance. Results: A total of 1112 adult patients underwent alpha-gal IgE testing and 359 (32.3%) were positive. Gastrointestinal symptoms were similar in those positive and negative for alpha-gal seroreactivity. Of the 359 alpha-gal–positive patients, 122 had follow-up data available and 82.0% of these improved on a diet free of mammalian products. Few patients reported hives (3.9%) or bronchospasm (2.2%). Serum alpha-gal IgE titers ranged from 0.1 to >100 kU/L, with an average of 3.43 kU/L and a median of 0.94 kU/L. Conclusions: Clinicians practicing in the region of the Lone Star tick habitat need to be aware that patients with IgE to alpha-gal can manifest with isolated abdominal pain and diarrhea, and these patients respond well to dietary exclusion of mammalian products.