Alpha-gal syndrome: Red meat allergy linked with tick

What is Alpha-gal syndrome? Alpha-gal syndrome is a type of serious food allergy that makes people allergic to red meat and other products made from mammals. It occurs most often in adults bitten by certain types of ticks and the symptoms range from mild to severe and vary over time.

The recent discovery of a tick-acquired mammalian meat allergy, called AGS, actually represents the synthesis of several seemingly disparate medical mysteries. Soumya Reddy, Department of Dermatology, University of Virginia, Charlottesville, Virginia, and colleagues noted severe infusion reactions to the monoclonal antibody (mAb) cetuximab to be among the first pieces of the puzzle. The occurrence of reactions during the first infusions suggested prior sensitization to the culprit allergen.

Clinically, AGS presents with abdominal pain, urticaria, nausea, and occasionally anaphylaxis, and has wide inter- and intra-personal variability. Urticaria is the most frequently reported symptom though angioedema and gastrointestinal symptoms are common as well. Alcohol intake and exertion are thought to worsen symptoms.

AGS can be easily confused with other causes of urticaria and anaphylaxis, such as mast cell activation syndrome (MCAS) and chronic spontaneous urticaria (CSU) because symptom onset is generally delayed by 2 to 6 hours after meat consumption.

Diagnosis poses a challenge for dermatologists unfamiliar with AGS. AGS diagnosis relies on a combination of clinical history, positive alpha-gal IgE blood testing and improvement on a mammalian-restricted diet. 

Management of the syndrome centres primarily on avoidance of mammalian meats (and occasionally dairy and other products) as well as acute management of allergic symptoms. Dietary counselling is imperative for all AGS patients. Most patients should completely avoid red meats, including pork, beef, lamb, goat, and rabbit, as well as organ meat and pork gut sausage casings. Avoidance of gelatin and dairy products may be necessary for the minority of patients who do not respond to red meat avoidance alone. Epinephrine is being recommended for patients with severe disease

Of note, it is the Lonestar tick in the US, which is common in the southeastern states that transmits the syndrome, as opposed to the deer tick, which commonly transmits Lyme disease and is endemic to the northeast region.

Reference:

Reddy, S., Yi, L., Shields, B., Platts-Mills, T., Wilson, J., & Flowers, R. H. (2023). Alpha-gal syndrome: A review for the dermatologist. Journal of the American Academy of Dermatology, 89(4), 750-757. https://doi.org/10.1016/j.jaad.2023.04.054