Acute/baseline ratios of all 3 MC mediator metabolites can enhance diagnosis and management of mast cell activation syndrome

Abstract

Background

Mast cell (MC) activation syndrome (MCAS) can be a challenge to diagnose and treat despite the near continuous appearance of publications outlining specific criteria. Follow-up of the clinical responses to treatment is often lacking, and confirmation that leukotriene C₄ (LTC₄) is an active participant in MCAS has been overlooked.

Objective

Three patients with MCAS characterized by anaphylaxis are presented to illustrate (1) the value of contemporaneous urinary mediator sampling during MCAS in addition to serum tryptase measurements and (2) substantiation of the fact that not only can LTC₄ (measured metabolite LTE₄) be the highest metabolite measured, but (3) blockade of the LTE₄ receptor can contribute to symptom prevention.

Method

The study methods comprised clinical review and quantitation of acute and baseline levels of tryptase and urinary MC mediators.

Results

The cases of 3 patients with MCAS are reviewed. In the first case, vespid sting–induced anaphylaxis was associated with a marked increase in the LTE₄ excretion. The addition of montelukast was instituted, and subsequent stings did not evoke symptoms. In the second case, acute measurements showed substantial increased levels of (2,3-dinor)-11β-prostaglandin F_2α, and LTE₄. The addition of aspirin plus montelukast prevented subsequent attacks. The third case documents a perioperative anaphylactic event with an acute/baseline LTE₄ ratio far higher than those of tryptase or other metabolites.

Conclusions

The value of measuring all 3 MC mediator metabolites during MCAS should not be overlooked. These measurements can facilitate the successful prevention of attacks. Furthermore, results from these tests show that histamine is often a minor player, whereas acute/baseline levels of the metabolites of LTC₄ and prostaglandin D₂ are frequently much higher, warranting nonantihistamine treatment.