Researchers detailed the case of a patient with systemic mastocytosis who had an anaphylactic reaction to galactose-α-1,3-galactose (alpha-gal) in a study published in Annals of Allergy, Asthma & Immunology. 

The case presents a 20-year-old man with recurrent episodes of hypotension, presyncope, and syncope. Initial investigations did not uncover an underlying cause. He then moved to a different state and did not experience these symptoms for the next 6 years. 

However, in 2015, he was admitted under the suspicion of sepsis secondary to an infected pilonidal cyst. Laboratory investigations revealed tryptase levels greater than 30. A bone marrow biopsy established the diagnosis of indolent systemic mastocytosis. 

The patient’s physicians started him on antihistamines, which allowed him to be free from anaphylactic episodes for a period of time. However, the patient later reported having weekly anaphylactic episodes. These episodes were often accompanied by severe hypotension and required more than one dose of epinephrine to resolve. 

Read more about systemic mastocytosis etiology 

The patient’s physicians increased his antihistamine regime, but his anaphylactic episodes persisted. This led them to conduct additional investigations, which revealed that he had elevated alpha-gal-specific immunoglobulin E. This indicates that the patient had an allergy to galactose-α-1,3-galactose (alpha-gal), a sugar found in most mammals. Mammalian meat avoidance resulted in the cessation of all anaphylactic episodes. 

“Our reports highlight the importance of considering food allergens, particularly alpha-gal, in locations with a high incidence of lone star tick bites, as possible triggers for recurrent anaphylaxis in patients with systemic mastocytosis,” the authors wrote. 

Patients with systemic mastocytosis often suffer from anaphylactic reactions; hence, this patient’s specific anaphylaxis to alpha-gal could have easily been overlooked had it not been for his frequent anaphylactic episodes. This case study also suggests that underlying systemic mastocytosis may result in a more acute alpha-gal reaction. 


Matthew S, Fadugba O. Systemic mastocytosis with concurrent alpha-gal associated anaphylaxis. Ann Allergy Asthma Immunol. Published online November 10, 2022. doi:10.1016/j.anai.2022.08.743