Case Report: Mast cell anergy: absence of symptoms after accidental re-exposure to amoxicillin/clavulanic acid 3 days after anaphylaxis

Empty mast cell syndrome, also named post anaphylaxis mast cell anergy (PAMA), is a temporary state of loss of mast cell responsiveness after a severe immediate hypersensitivity reaction. In this study, we describe a case of PAMA after accidental re-exposure to amoxicillin in a patient who developed severe anaphylaxis to this drug three days earlier in the operating room. To our knowledge, this report is the second to document this phenomenon.

Empty mast cell syndrome: fallacy or fact?

Post-anaphylaxis mast cell anergy (PAMA), commonly referred to as 'empty mast cell (MC) syndrome', is a state of temporary loss of cutaneous MC reactivity in the immediate aftermath of anaphylaxis. Data relating to this condition are sparse and the incidence rate is currently unknown. PAMA has been described only in a few published case reports in the context of hymenoptera venom allergy and perioperative anaphylaxis. Best practice guidelines regarding optimal timing for performing skin tests postanaphylaxis are largely based on expert opinion, and allergy work-up has been recommended after 4-6 weeks postanaphylaxis to avoid false-negative results.This article provides a review of clinical literature surrounding PAMA, critically evaluates intracellular events in MCs from in vitro data and hypothesises regarding plausible immune mechanisms. There are no published data to directly explain molecular mechanisms underlying this phenomenon. Although not evidence based, PAMA has been attributed to depletion of MC granules following anaphylaxis. It is also plausible that exposure to high allergen concentrations in anaphylaxis can induce a temporary shift in MCs towards dominance of inhibitory signalling pathways, thus contributing to a state of transient hyporesponsiveness observed in some patients. Other potential contributory factors for reduced MC reactivity include downregulation of FcεRI expression, cross-linking of FcεRI to the inhibitory, low-affinity IgG receptors and administration of pharmacotherapeutic agents for anaphylaxis treatment. It is likely that this interesting phenomenon can be explained by a combination of these proposed mechanisms in addition to other genetic/host factors that have not yet been identified.

Differential effects of beta2-adrenoceptor desensitization on the IgE-dependent release of chemical mediators from cultured human mast cells

In the present study, we examined the inhibitory effects of the beta2-adrenoceptor agonists isoproterenol, salbutamol, fenoterol, and clenbuterol, on the release of chemical mediators from cultured human mast cells after prolonged treatment with the agonists. Although preincubation of sensitized mast cells for 10 min with beta2-adrenoceptor agonists potently inhibited mediator release, prolongation of the preincubation period up to 240 min attenuated the inhibition. The attenuation of histamine release inhibition was potent when compared with that of prostaglandin D2 (PGD2) and cysteinyl leukotriene (LT) release inhibition. In contrast, forskolin inhibited mediator release and the inhibition increased gradually in proportion to the preincubation period. The reduced inhibition by the beta2-adrenoceptor agonists was compensated for by simultaneous treatment with cholera toxin. The beta2-adrenoceptor agonists elevated intracellular cAMP levels after 10-min incubation and the elevated levels were almost comparable to those after 240-min incubation. Forskolin elevated the intracellular cAMP levels more potently after incubation for 240 min than after 10 min. When mast cells were incubated for 3 d with the beta2-adrenoceptor agonists, similar attenuation of mediator release inhibition was observed. Elevation of intracellular cAMP levels was also attenuated, although beta2-adrenoceptor mRNA expression was potentiated. The present results collectively indicate that the attenuation of mediator release inhibition by beta2-adrenoceptor agonists under the present experimental conditions involves uncoupling between beta2-adrenoceptors and Gs proteins. Furthermore, the beta2-adrenoceptor desensitization causes differential attenuating effects on the inhibition of histamine, PGD2, and LT release, suggesting that downstream events involved in each inhibitory pathway have different sensitivity to receptor desensitization.