The same patient had presented with anaphylaxis two years prior. At that time, she was found to have an Amblyomma americanum ‘lone star’ tick (identified by pathology) attached to her abdomen. As for the source of patient’s anaphylaxis, she did endorse handling and eating ‘red meat’ several hours prior to presentation. The patient followed up with an allergist and was found to have an elevated total serum IgE at 773 kU/L (normal< 114). Serum analysis for specific allergens was positive for pork, lamb and beef. However, a galactose- alpha- 1, 3- galactose IgE (Alpha- Gal) test was negative. The patient was advised to stop eating red meat, and her symptoms improved.
One year later, the patient started introducing meat back into her diet. She subsequently re-presented with anaphylaxis two times afterwards, this being her third admission. The Alpha- Gal test was repeated, and again it was negative.
Discussion: People bitten by the lone star tick may develop IgE antibodies to galactose- alpha- 1, 3- galactose (Alpha- Gal), a carbohydrate (not protein) expressed in red meat. Upon exposure to red meat, these sensitized individuals may develop a delayed anaphylactic reaction, usually 3 to 6 hours after ingestion. The incidence of developing this antibody is unknown, as doctors are not required to test for it in tick-bitten individuals. Also the tick-induced antibody may be temporary or permanent. If antibodies are indeed present, their levels may fluctuate.
This patient’s presentation is consistent with a classic lone star tick-induced delayed anaphylaxis to red meat (first presentation of anaphylaxis late in life, symptoms occurred hours after ingestion and symptoms improved with stopping red meat intake). Yet the patient’s Alpha- Gal test was negative twice. The Alpha- Gal test is reportedly highly specific (although exact values for the assay are not found in the literature). As this symptomatic patient’s Alpha- Gal test was repeatedly negative, this brings into question the existence of a false negative antibody test or more likely, an antibody negative variant of this allergy.
Conclusions: Patients bitten by the Amblyomma americanum ‘lone star’ tick may develop allergies to red meat, specifically in the form of delayed anaphylaxis. Although there is testing available for such, via a galactose- alpha- 1, 3- galactose IgE (Alpha- Gal) test, this case suggests the test may not be sensitive or that an antibody negative variant of this allergy may exist.