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JACI Highlights - February 2009
Beware the Alpha gal: Delayed anaphylaxis, angioedema or urticaria after consumption of red meat
Scott P. Commins, MD, PhD, Shama M. Satinover, MS, Jacob Hosen, BS, Jonathan Mozena, MD, Larry Borish, MD, Barrett D. Lewis, MD, Judith A. Woodfolk, MBChB, PhD and Thomas A.E. Platts-Mills, MD, PhD
Anaphylaxis is an increasingly common, potentially deadly outcome of allergic events. For people with very serious allergies, it is important to identify the substances that cause a severe reaction so that those allergens can be avoided, reducing the risk of future episodes.
We typically tell our patients that it is protein in things that cause allergic reactions — whether it’s the protein in a food, pollen, dander or venom — but not fats (like oil) or carbohydrates (like sugar). We also tell patients that reactions typically occur within minutes of exposure. However, recent research has skewed our perspective somewhat, showing that a carbohydrate epitope, alpha-gal, which is commonly present on mammalian proteins, is capable of eliciting serious, even fatal, allergic reactions.
In a study published in the February 2009 issue of The Journal of Allergy and Clinical Immunology, Commins et al. report on 24 patients with IgE antibodies to alpha-gal who had been treated for anaphylaxis, angioedema or urticaria. These patients had reported serious allergic symptoms 3 to 6 hours after eating beef, pork or lamb and when tested, they demonstrated a consistent pattern of both positive skin prick reactions and serum IgE antibodies to alpha-gal. A distinct commonality in the cases is that the patients’ onset of symptoms took significantly longer to manifest than is normally expected with food allergies.
Most anaphylactic reactions happen because of IgE response to proteins and this report of severe allergy to a carbohydrate is really different. That makes this an especially intriguing finding. What causes the production of IgE antibodies to alpha-gal in these adult patients? And why are reactions to meat delayed for several hours? There are questions to be answered in future studies. In the meantime, this report seems to break some new and important ground.
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