University of North Carolina Chapel Hill, North Carolina
Introduction: Galactose-α-1,3-galactose (alpha-gal) allergy is an IgE-mediated reaction to mammalian meat and dairy, with symptoms typically developing 3 to 6 hours after ingestion. Alpha-gal allergy with isolated gastrointestinal (GI) symptoms (abdominal pain, diarrhea, vomiting) without urticaria or anaphylaxis has been described.
Case Description/Methods: A 49-year-old male presented to GI clinic with years of episodic cramping abdominal pain and 4-6 diarrheal stools daily. Colonoscopy, EGD, CT abdomen, and hydrogen breath testing were unrevealing. We diagnosed irritable bowel syndrome. Rifaximin briefly relieved symptoms. He did not tolerate tricyclic antidepressants. Serum alpha-gal IgE level was found to be elevated at 0.27 kU/L (reference range, < 0.1 kU/L) after the patient reported past tick bites. The patient stopped eating mammalian meat and symptoms improved but continued. He further excluded gelatin in the form of gummy bears, dairy, and carrageenan, which led to near resolution of symptoms. At a visit 2 years following allergy diagnosis, he reported one formed stool daily and no chronic abdominal pain. Self-challenging with foods that have small amounts of alpha gal, like a handful of gummy bears, had resulted in severe abdominal cramping.
Discussion: The diagnosis of GI alpha-gal syndrome can be challenging because of delayed onset of symptoms after eating mammalian products, nonspecific GI complaints on presentation, and overlap with preexisting GI diseases. While sensitization is believed to be caused by a bite from the Lone Star tick, not all patients report a history of tick bites. Further studies are needed to better characterize GI alpha gal, but two cohort studies found that ~75% of patients improved on a diet free of mammalian products. These diets are somewhat ill-defined in how strict they are, particularly whether they are just free of mammalian meat or all products containing alpha-gal. A stepwise approach is recommended, starting with mammalian meat, then dairy, and then gelatin, gelatin capsules, and mammalian food additives if symptoms persist. Our patient experienced improvement in symptoms with elimination of mammalian meat from his diet, but no resolution until he eliminated all alpha-gal, particularly gelatin and carrageenan. This case highlights the importance of a thorough history, increased awareness of foods containing alpha-gal, and the need for future prospective studies for improving early recognition and treatment of GI alpha gal.
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