TOXICOLOGY QUESTION OF THE WEEK
August 25, 2023
Comments in response to Alpha-gal Allergy
In response to the previous Question of the Week, Dr. Cosby Stone Jr. MD, MPH, made the following comments:
The observed prevalence of confirmed alpha-gal cases across Vanderbilt clinics has been steadily increasing year over year, as has the number of cases confirmed annually. https://pubmed.ncbi.nlm.nih.gov/37080457/ Among those patients, 30% report anaphylaxis symptoms, around 50% report urticaria/angioedema and GI symptoms, and 20% report only GI symptoms.
We at Vanderbilt, and other centers (such as North Carolina), have more clearly identified that there is a phenotype of alpha-gal syndrome that presents with GI symptoms only. A study we did in our pediatric GI clinics suggests that in our area between 5-10% of patients with medically unexplained symptoms of recurrent abdominal pain, diarrhea, nausea, vomiting might have alpha-gal syndrome as a contributory factor. https://pubmed.ncbi.nlm.nih.gov/36995329/
However, it’s also vitally important to recognize that a whole lot of patients are sensitized but will have no symptoms. (up to 20% of Tennesseans). https://pubmed.ncbi.nlm.nih.gov/18337601/ Among those who will have detectable IgE antibodies against alpha-gal, the vast majority will have no symptoms of alpha-gal at all (maybe only 1% of those who have IgE antibodies against alpha-gal).
Therefore, routine blood test screening of asymptomatic people for alpha-gal currently looks like a bad idea, but in the presence of the right symptoms, your patients will really appreciate you for considering it. If you do find that positive blood test for alpha-gal, a consistent symptomatic improvement with avoidance of mammalian meat is usually the best sign of a right diagnosis. In borderline cases with lower severity symptoms, we can also consider observed challenges in the allergy clinic to help confirm or disprove the diagnosis. The Vanderbilt Allergy Clinics are always happy to help you manage this allergy and assist in the patient care.
Question submitted by Dr. Cosby Stone Jr. MD, MPH, Assistant Professor in Allergy/Immunology, VUMC.
Comment: One of the best parts of the Question of the Week is the comments we get from our experts who read the Question. Thanks Dr. Stone. ds
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DONNA SEGER, MD
Department of Medicine
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