Serum Baseline Tryptase Level as a Marker for the Severity of Anaphylaxis

Alpha-Tryptase as a Risk-Modifying Factor for Mast Cell-Mediated Reactions

PURPOSE OF REVIEW

To provide an overview on the current understanding of genetic variability in human tryptases and summarize the literature demonstrating the differential impact of mature tryptases on mast cell-mediated reactions and associated clinical phenotypes.

RECENT FINDINGS

It is becoming increasingly recognized that tryptase gene composition, and in particular the common genetic trait hereditary alpha-tryptasemia (HαT), impacts clinical allergy. HαT has consistently been associated with clonal mast cell disorders (MCD) and has also been associated with more frequent anaphylaxis among these patients, and patients in whom no allergic trigger can be found, specifically idiopathic anaphylaxis. Additionally, more severe anaphylaxis among Hymenoptera venom allergy patients has been linked to HαT in both retrospective and prospective studies. An increased relative number of α-tryptase-encoding gene copies, even in the absence of HαT, has also been associated with systemic mastocytosis and has been shown to positively correlate with the severity of mast cell-mediated reactions to vibration and food. These findings may be due to increased generation of α/β-tryptase heterotetramers and differences in their enzymatic activity relative to β-tryptase homotetramers. HαT is a naturally occurring overexpression model of α-tryptase in humans. Increased relative α-tryptase expression modifies immediate hypersensitivity symptoms and is associated with more frequent and severe mast cell-mediated reactions, ostensibly due to increased α/β-tryptase heterotetramer production.

Challenge-confirmed diagnosis restores quality of life in cofactor-dependent wheat allergy

BACKGROUND

Food allergies including cofactor-dependent allergies such as cofactor-dependent wheat allergy (CDWA) decrease the quality of life (QOL) of patients.

OBJECTIVE

To define the health-related QOL and fears in patients with CDWA and to evaluate the impact of diagnosis confirmation by oral challenge test (OCT).

METHODS

Patients with CDWA diagnosed by clinical history, sensitization, and OCT were invited to participate. Clinical characteristics, patients' fears, self-perceived overall QOL, the Food Allergy Quality of Life Questionnaire-Adult Form score, and the risks and benefits of OCT were evaluated after the final diagnosis.

RESULTS

A total of 22 adults with CDWA (13 male, 9 female; mean age 53.5 years; median 5 years until diagnosis) were included. Specific immunoglobulin E (IgE) levels for gluten proteins were inversely correlated with the reaction threshold (P < .05). Higher reaction severity in the patients' histories correlated with increased basal serum tryptase levels (P = .003) and gluten and gliadin specific IgE (P < .05), but not to QOL. After the first allergic reaction, patients reported a drop in QOL (P < .001). Challenge-confirmed diagnosis and medical consultation could restore the patients' QOL (P < .05) and reduce their fear of further reactions (P < .01). No severe reactions occurred during OCT, which was rated as not stressful and highly beneficial. Compared with patients with CDWA diagnosed without OCT in the literature, health-related QOL was less impaired (mean Food Allergy Quality of Life Questionnaire-Adult Form score 3.8), especially regarding the emotional impact (P < .001 vs existing literature).

CONCLUSION

Until final diagnosis, patients with CDWA have a severe physical and psychological burden. OCT is a safe method to confirm the diagnosis, restore the patients' severely affected QOL, and reduce their fear of further reactions.

Anaphylaxis: Advances in the Past 10 Years

In the past 10 years, anaphylaxis has grown into its own special area of study within Allergy-Immunology, both at the bench and at the bedside. This review focuses on some of the most clinically relevant advances over the past decade. These include simplified and more inclusive diagnostic criteria for adults and children, uniform definition of biphasic anaphylaxis, and improved systems for objective severity grading. Studies reported in the past decade have led to improved understanding of normal and abnormal regulation of mast cell function, translating into better diagnostic and therapeutic approaches to patients with anaphylaxis. Research has provided improved recognition and treatment of mast cell disorders and has identified a new condition, hereditary α-tryptasemia, that may impact anaphylactic syndromes. We have learned to recognize new causes (α-gal), new pathways (Mas-related G protein-coupled receptor-X2), and many risk factors for severe anaphylaxis. The stability of epinephrine in autoinjectors was reported to be very good for several years after the labeled expiry date, and it can tolerate freezing and thawing. Repeated and prolonged exposure to excessive heat leads to degradation of epinephrine activity. New treatments to prevent severe anaphylaxis have been described, using new ways to block the IgE receptor or modulate intracellular signaling pathways.

A typical case had rare immediate and delayed red man syndrome multiple times after norvancomycin injection: A case report

BACKGROUND

Red man syndrome (RMS) is an adverse effect of vancomycin that usually occurs within minutes to tens of minutes after infusion. Previous literature reported that RMS rarely occurs again after the infusion speed is controlled.

METHODS

We report a case of immediate and delayed RMS that presented with fever, persistent lower extremity rash, shock, lymphadenopathy and pulmonary edema. This patient subsequently diagnosed with Sjögren's Syndrome, the time from NVCM infusion to RMS onset of this case ranged from 10 minutes to 54 hours, which are all rare in clinic and hard to distinguish severe RMS and IgE-mediated anaphylaxis.

RESULTS

After multidisciplinary consultation, the patient was diagnosed with RMS based on clinical manifestations and laboratory results. Patients' symptoms, signs, body temperature and disease progress were monitored, and an active search for causes was conducted. After a 20-day treatment, all the symptoms disappeared, the patient was transferred to immunology department to treat SS.

CONCLUSION SUBSECTIONS

We reported a patient repeatedly developed fever and even shock when the infusion speed is normal, which was rare and similar as anaphylaxis. Therefore, the progression of RMS and its differentiation from allergy need to be further studied.

Clinical utility of serum tryptase levels in pediatric anaphylaxis

Introduction: This study aimed to evaluate the preliminary diagnosis, demographic characteristics, and outcomes of patients whose serum total tryptase levels were measured while in a tertiary pediatric hospital and to ascertain the role of serum tryptase levels in the etiology, diagnosis, severity, and course of systemic anaphylaxis. Methods: Patients ages between 1 month and 17 years who were followed up in the pediatric emergency department or as inpatients and with a diagnosis of immediate-type reactions between September 1, 2019, and August 31, 2021, were included in the study. Patient data were obtained retrospectively by examination of medical records and patient observation forms. Results: It was determined that serum tryptase levels were measured in a total of 310 patients during the study period. One hundred and fifty-five patients who met the defined diagnostic criteria were named as the anaphylaxis group and their data were detailed. The serum tryptase elevation was detected in 15.5% of the patients among the samples that met the anaphylaxis diagnostic criteria. No relationship was found between the serum total tryptase levels, the triggering factor, and the severity of anaphylaxis. Discussion: Anaphylaxis is a complex syndrome that involves different phenotypes that develop with various triggers in which different immunologic pathways, cell types, and mediators play a role. Serial measurements, including the basal value measured at least 24 hours after the symptoms disappear, are useful to confirm the diagnosis and guide the diagnostic tests during the follow-up, especially allergy evaluation.

Resolving the genetics of human tryptases: implications for health, disease, and clinical use as a biomarker

PURPOSE OF REVIEW

To discuss our evolving understanding of the genetic variation in human tryptases and recent advances in associated clinical phenotypes.

RECENT FINDINGS

Serum tryptase levels have long been used as biomarkers in clinical practice to diagnose mast cell-associated disorders and mast cell-mediated reactions but the contribution of specific secreted isoforms of human tryptases and their role(s) in health and disease has only recently begun to be illuminated. It is now recognized that hereditary alpha-tryptasemia (HαT) is a common genetic trait and the commonest cause for elevated basal serum tryptase (BST), where it can both contribute to mast cell-associated phenotypes, and potentially confound their correct diagnosis. Expression of different tryptase isoforms is now recognized to be associated with specific clinical phenotypes including clonal and nonclonal mast cell-associated disorders as well as certain asthma endotypes. These disparate impacts on clinical disorders may result from differences in enzymatic activities of mature α-tryptases and β-tryptases, and the unique substrate profile and stability of heterotetrameric mature α/β-tryptases recently described to naturally occur.

SUMMARY

Variable copy number and isoform expression of tryptases differentially impact diseases and reactions associated with mast cells in humans. Recent advances in understanding of genetics governing BST levels have refined our understanding and the clinical use of this biomarker. In the future, incorporation of tryptase genotyping will likely be integral to the work-up and trial design of patients with phenotypes impacted by mast cells ranging from asthma to mastocytosis.

Reducing the sting: Diagnosis and management of Hymenoptera venom allergy

ABSTRACT

Hymenoptera species include stinging insects such as wasps, hornets, bees, and fire ants. Allergic reaction to the venom of these insects is a common presenting complaint for patients in primary care and emergency medicine during warmer months. Patients' clinical presentations may vary, and clinicians must identify the type of reaction to determine treatment and follow-up plans. Treatment of patients allergic to Hymenoptera venom should be individualized based on risk factors, reaction type, and associated comorbidities. This article reviews common features of clinical presentation, diagnosis, and the current mainstays in management of Hymenoptera venom allergy.

Hereditary Alpha-Tryptasemia: a Commonly Inherited Modifier of Anaphylaxis

PURPOSE OF REVIEW

Hereditary alpha-tryptasemia (HαT) is an autosomal dominant genetic trait and a common cause of elevated basal serum tryptase in Western populations. It is a risk factor for severe anaphylaxis among individuals with venom allergy and an established modifier of anaphylaxis and mast cell mediator-associated symptoms among patients with systemic mastocytosis. Understanding the physiology of tryptases and how this may relate to the clinical features associated with HαT is the first step in identifying optimal medical management and targets for novel therapeutics.

RECENT FINDINGS

HαT prevalence is increased in both clonal and non-clonal mast cell-associated disorders where it augments symptoms of immediate hypersensitivity, including anaphylaxis. The unique properties of naturally occurring α/β-tryptase heterotetramers may explain certain elements of phenotypes associated with HαT, though additional mechanisms are being evaluated. This review provides an overview of the clinical and translational studies that have identified HαT as a modifier of mast cell-associated disorders and anaphylaxis and discusses mechanisms that may potentially explain some of these clinical findings.

Mast cell tryptases in allergic inflammation and immediate hypersensitivity

Dysregulated mast cell-mediated inflammation and/or activation have been linked to a number of human diseases, including asthma, anaphylaxis, chronic spontaneous urticaria, and mast cell activation syndromes. As a major mast cell granule protein, tryptase is a biomarker commonly used in clinical practice to diagnose mast cell-associated disorders and -mediated reactions, but its mechanistic roles in disease pathogenesis remains incompletely understood. Here, we summarize recent advances in the understanding of human tryptase genetics and the effects that different genetic composition may have on the quaternary structure of tetrameric mature tryptases. We also discuss how these differences may impact clinical phenotypes including allergic inflammation, immediate hypersensitivity, and others seen in patients with mast cell-associated disorders. With the increased application of next-generation sequencing, we foresee that human genetic approaches will be a major focus of understanding human tryptase functions in various human mast cell disorders and in new therapeutic development.

Proceedings from the Inaugural American Initiative in Mast Cell Diseases (AIM) Investigator Conference

The American Initiative in Mast Cell Diseases (AIM) held its inaugural investigator conference at Stanford University School of Medicine in May 2019. The overarching goal of this meeting was to establish a Pan-American organization of physicians and scientists with multidisciplinary expertise in mast cell disease. To serve this unmet need, AIM envisions a network where basic, translational, and clinical researchers could establish collaborations with both academia and biopharma to support the development of new diagnostic methods, enhanced understanding of the biology of mast cells in human health and disease, and the testing of novel therapies. In these AIM proceedings, we highlight selected topics relevant to mast cell biology and provide updates regarding the recently described hereditary alpha-tryptasemia. In addition, we discuss the evaluation and treatment of mast cell activation (syndromes), allergy and anaphylaxis in mast cell disorders, and the clinical and biologic heterogeneity of the more indolent forms of mastocytosis. Because mast cell disorders are relatively rare, AIM hopes to achieve a coordination of scientific efforts not only in the Americas but also in Europe by collaborating with the well-established European Competence Network on Mastocytosis.

What is new in anaphylaxis?

Available information suggests that anaphylaxis must be promptly recognized keeping in mind the airway patency, breathing (ventilation and respiration), circulation and mental status and treated. The first treatment is adrenaline. After successful treatment of an anaphylactic episode, attention must be paid to the prevention of early recurrences (biphasic anaphylaxis) and assessment of causes. Children should not be discharged before prescribing self-injectable adrenaline and explain how and under what circumstances it must be injected, An action plan must be communicated to their communities. Inform the school about potential reactions, how to prevent them and avoidance measures. (www.actabiomedica.it)

Mast cell activation in the context of elevated basal serum tryptase: genetics and presentations

PURPOSE OF REVIEW

To describe inherited and acquired genetic variants and clinical entities associated with increased basal serum tryptase (BST), distinguish these levels from those which acutely rise due to mast cell activation, and finally to characterize the association between chronically elevated basal serum tryptase and episodic mast cell activation.

RECENT FINDINGS

Hereditary alpha-tryptasemia is a commonly inherited genetic cause for basally elevated serum tryptase and explains elevated BST in many individuals who do not have evidence of clonal myeloid or mast cell disease. When clonal myeloid disease is present, BST may be elevated and can be a biomarker of a number of disparate disorders of the myeloid compartment. Elevated BST is most commonly caused by hereditary alpha tryptasemia but may also be indicative of clonal myeloid disease. Clinical reports suggest that elevated BST is associated with increased risk for more severe systemic allergic reactions to a number of eliciting agents and exposures. Additional studies are needed to determine the role that inherited or acquired genetic variants associated with elevated BST and clonal or non-clonal myeloid diseases may play in these reactions.

Increased Basal Blood Histamine Levels in Patients with Self-Reported Hypersensitivity to Non-Steroidal Anti-Inflammatory Drugs

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) represent one of the most prevalent causes of drug hypersensitivity reactions (DHRs), yet the underlying processes are far from clear. Despite the established role of histamine in allergic reactions, its precise implication in DHRs is elusive.

OBJECTIVES

This study aimed to explore the connection of basal blood histamine levels to the reported NSAID hypersensitivity.

METHODS

Sixteen patients reporting hypersensitivity reactions to a single or multiple NSAIDs and/or paracetamol and 18 healthy volunteers serving as the normal control group enrolled in the study. The medical history was recorded and histamine was quantified spectrophotofluorometrically in whole peripheral blood and plasma.

RESULTS

Compared to the normal group, plasma but not whole blood histamine levels were significantly higher in patients (p < 0.001), mainly in the subgroup reporting hypersensitivity to a single agent (p < 0.001). Plasma histamine levels were significantly correlated with the culprit drug selectivity for cyclooxygenase (COX) isozymes (p < 0.001), with higher levels being obtained in patients reporting reactions to COX-1 than to COX-2 selective inhibitors (p < 0.05).

CONCLUSIONS

The findings provide first evidence connecting basal blood histamine levels to the reported NSAID-triggered DHRs. Prospective studies are expected to decipher the contribution of histamine-associated parameters to the mechanisms underlying DHRs.

Recent Advances in Clinical Allergy and Immunology 2019

The immune system has vital functions for homeostasis and host defense. Thus, imbalances of the immune system whether associated with allergy, hypersensitivity, or autoimmunity are of great importance, as is manifest from common diseases such as atopic diseases, urticaria, and angioedema, and drug hypersensitivity reactions. These can affect patients' quality of life and can generate high costs for health care. Epidemiological studies have provided evidence for changing patterns of allergic diseases caused by lifestyle and climate changes which have consequences for medical care. Deeper insights into the pathogenesis of allergic/immunologic diseases, combined with novel technologies, provide improved diagnostic options and treatment measures. This review will summarize novel aspects of the epidemiology, pathogenic mechanisms, as well as disease management in the fields of allergy and clinical immunology.

Refractory Anaphylaxis: Data From the European Anaphylaxis Registry

Refractory anaphylaxis (unresponsive to treatment with at least two doses of minimum 300 μg adrenaline) is a rare and often fatal hypersensitivity reaction. Comprehensive data on its definition, prevalence, and risk factors are missing. Using the data from the European Anaphylaxis Registry (11,596 cases in total) we identified refractory anaphylaxis cases (n = 42) and analyzed these in comparison to a control group of severe anaphylaxis cases (n = 4,820). The data show that drugs more frequently elicited refractory anaphylaxis (50% of cases, p < 0.0001) compared to other severe anaphylaxis cases (19.7%). Cases elicited by insects (n = 8) were more often due to bees than wasps in refractory cases (62.5 vs. 19.4%, p = 0.009). The refractory cases occurred mostly in a perioperative setting (45.2 vs. 9.05, p < 0.0001). Intramuscular adrenaline (as a first line therapy) was administered in 16.7% of refractory cases, whereas in 83.3% of cases it was applied intravenously (significantly more often than in severe anaphylaxis cases: 12.3%, p < 0.0001). Second line treatment options (e.g., vasopression with dopamine, methylene blue, glucagon) were not used at all for the treatment of refractory cases. The mortality rate in refractory anaphylaxis was significantly higher (26.2%) than in severe cases (0.353%, p < 0.0001). Refractory anaphylaxis is associated with drug-induced anaphylaxis in particular if allergens are given intravenously. Although physicians frequently use adrenaline in cases of perioperative anaphylaxis, not all patients are responding to treatment. Whether a delay in recognition of anaphylaxis is responsible for the refractory case or whether these cases are due to an overflow with mast cell activating substances—requires further studies. Reasons for the low use of second-line medication (i.e., methylene blue or dopamine) in refractory cases are unknown, but their use might improve the outcome of severe refractory anaphylaxis cases.