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Potentially life-threatening emergency
Alpha-gal syndrome
Other Resources UpToDate PubMed
Potentially life-threatening emergency

Alpha-gal syndrome

Contributors: Paritosh Prasad MD, Susan Burgin MD
Other Resources UpToDate PubMed

Synopsis

Emergent Care / Stabilization:
Acute management involves administration of intramuscular epinephrine and circulatory support with intravenous (IV) crystalloids.
  • Immediately assess the patient's airway, breathing, circulation, and mental status.
  • Administer epinephrine 0.2-0.5 mg (in adults) or 0.01-0.3 mg/kg (in children) intramuscularly in a large muscle belly (eg, anterolateral thigh) every 5-10 minutes to manage symptoms.
  • Support circulatory collapse with IV fluid resuscitation concurrent with epinephrine as above.
Diagnosis Overview:
Tick bites from some Amblyomma (lone star tick) and Ixodes (and possibly Haemaphysalis) species have been associated with the subsequent development of immunoglobulin E (IgE) antibodies to alpha-gal (galactose-alpha-1,3-galactose), a mammalian oligosaccharide. Presence of IgE antibodies to alpha-gal is associated with 2 distinct forms of anaphylaxis in the United States, Europe, Asia, and Australia.

Individuals with elevated IgE titers to alpha-gal have experienced symptoms of urticaria, gastrointestinal distress, angioedema, and/or anaphylaxis immediately or 3-6 hours (delayed onset) after ingesting mammalian meat (eg, beef, pork) or being exposed to alpha-gal in products made from mammals (eg, medications, cosmetics, vaccines, gelatin, milk products). Implicated tick bites have been noted to be associated with pruritus for 2 or more weeks.

The other reaction seen in patients with IgE to alpha-gal is an immediate onset of anaphylaxis during first exposure to IV cetuximab, an epidermal growth factor receptor (EGFR) inhibitor used for the treatment of colorectal cancer, metastatic non-small cell lung cancer, and head and neck cancer.

A blood test for these IgE antibodies exists.

Delayed diagnosis and treatment of anaphylaxis of any cause predicts poor prognosis. Immediate management involves removal of the triggering allergen if possible, epinephrine by intramuscular injection, and further evaluation and management.

IgE to alpha-gal has been identified in some Sub-Saharan African populations where it is thought to be due to exposure to cestodes, nematodes, scabies, ticks, and a variety of other ectoparasites. Interestingly, however, there have been no reports of delayed anaphylaxis upon exposure to red meat in this population.

Per the US Centers for Disease Control and Prevention, the number of suspected alpha-gal syndrome cases in the United States has increased substantially since 2010, and states with established populations of lone star ticks are most affected (South, East, and Central United States), although suspected alpha-gal syndrome cases were also identified in areas outside of this tick's range.

Codes

ICD10CM:
Z91.014 – Allergy to mammalian meats

SNOMEDCT:
788781001 – Delayed allergy to red meat

Look For

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Other etiologies of Anaphylaxis
  • Food allergies (eg, Food protein-induced enterocolitis syndrome)
  • Urticaria

Best Tests

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Management Pearls

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Therapy

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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References

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Last Reviewed:09/11/2023
Last Updated:08/01/2023
Copyright © 2024 VisualDx®. All rights reserved.
Potentially life-threatening emergency
Alpha-gal syndrome
A medical illustration showing key findings of Alpha-gal syndrome (Overview) : Tick bite, Urticaria
Copyright © 2024 VisualDx®. All rights reserved.