ELEVATED HISTAMINE LEVELS WITH NORMAL TRYPTASE IN ANAPHYLAXIS

Abstract

<h3>Introduction</h3> The most commonly described pathway of anaphylaxis involves IgE mediated mast cell activation. Here we present three patients with elevated histamine, normal tryptase, and normal IgE. These findings suggest a non-mast-cell mediated pathway of anaphylaxis. All patients were placed on a low-histamine diet (LHD) following their anaphylaxis episodes with subsequent decrease in histamine and resolution of anaphylactic episodes. <h3>Cases Description</h3> The first patient was a 25-year-old male who presented to the emergency department with a histamine level of 6.0 (ng/mL). The patient experienced a second anaphylaxis episode a week later. Repeat histamine was 6.5. The patient was placed on a LHD, and follow-up testing demonstrated histamine of 1.6. The second patient was a 51-year-old male who presented to the emergency department for anaphylaxis. Laboratory studies after the event found histamine of 13.2, and the patient was subsequently placed on a LHD. Follow-up testing demonstrated histamine of 5.8. The third patient was a 33-year-old female that developed anaphylaxis after a patch test. Laboratory studies revealed histamine of >28.6. The patient was instructed to start a LHD. Subsequent testing demonstrated histamine of 10.8. <h3>Discussion</h3> Persistent elevation of histamine levels in the absence of elevated tryptase or IgE suggests a non-mast-cell mediated pathway of histamine release. Further studies should be performed in similar cases examining the potential of LHD as a treatment for anaphylaxis with elevated histamine and normal tryptase as LHD resulted in a decrease in histamine level and resolution of anaphylactic episodes.