Refractory Anaphylaxis: A New Entity for Severe Anaphylaxis

Mast Cell Disorders and Hymenoptera Venom-Triggered Anaphylaxis: Evaluation and Management

Patients with Hymenoptera venom allergy (HVA), especially those with severe anaphylaxis, frequently have concomitant clonal mast cell disease (MCD) in the form of systemic mastocytosis or monoclonal mast cell activation syndrome. Detection of clonal MCD is important because it will have significant consequences for managing HVA. Therefore, we recommend patients with HVA be systematically screened for clonal MCD. The pretest probability of clonal MCD can be assessed in a stepwise fashion starting with examination of the skin for typical monomorphic maculopapular cutaneous mastocytosis lesions; measurement of the baseline serum tryptase (BST) and tryptase genotyping for patients with BST greater than 11 ng/mL; followed by the Red Española de Mastocitosis score, which is calculated using anaphylaxis clinical features, BST, and the patient's sex. A bone marrow biopsy should be performed in patients with monomorphic maculopapular cutaneous mastocytosis, a Red Española de Mastocitosis score of 2 or greater, or an elevated BST based on tryptase genotype. Patients with HVA and a clonal MCD should be treated with immunotherapy directed against the Hymenoptera venom for which they are sensitized. For this high-risk subgroup of patients with HVA, it is recommended to continue immunotherapy for more than 5 years or indefinitely and to carry at least three epinephrine autoinjectors. Future studies should determine whether KIT D816V-selective tyrosine kinase inhibitors are effective at preventing or reducing the severity of Hymenoptera-venom triggered anaphylaxis in patients with clonal MCD.

Tryptase in drug-induced anaphylaxis: the need for acute and baseline values

PURPOSE OF REVIEW

The purpose of this narrative review was to summarize data and official recommendations purporting to paired tryptase determination in patients experiencing drug-induced anaphylaxis, published between January 1, 2023 and June 1, 2024.

RECENT FINDINGS

Three main lines of evidence obtained through paired acute and baseline tryptase determination were identified: diagnostic criterion for hypersensitivity reactions involving systemic mast cell activation; differential diagnostic criterion for hypersensitivity reactions involving other mechanisms of immediate reactions; and added value of acute and baseline tryptase levels for personalized management following drug-induced anaphylaxis: cause, risk of recurrence, underlying mast cell conditions including hereditary α-tryptasemia, familial clusters.

SUMMARY

The implementation of existing guidelines which consensually recommend paired tryptase measurement is a persistent unmet need hampering optimal diagnosis of drug-induced anaphylaxis and patient management. Another major unmet need is the lack of standardized recommendations for hereditary α-tryptasemia testing and counselling. Progress in this field is seen at a rapid pace, requiring significant efforts of continued medical education for practicing clinicians and laboratory specialists worldwide.

Anaphylaxis: Definition and criteria

Anaphylaxis is a systemic allergic reaction that may be severe and life-threatening. With more than a dozen anaphylaxis definitions proposed over the past several decades and several diagnostic criteria in circulation, there is a need for a multinational consensus definition to simplify management across specialties. Anaphylaxis diagnostic criteria are more alike than they are different, and approaches of the National Institute of Allergy and Infectious Disease, World Allergy Organization, and Brighton Collaborative help to add granularity and perspective to patient management. Anaphylaxis occurs across a spectrum of severity within populations, although, among individual patients, there is some evidence to suggest more consistency for an individual allergen. Still, severity is influenced by a number of factors that demonstrate variability: factors that relate to allergen triggers, patient characteristics, and treatments received. Severity of anaphylaxis impacts management, and recent guidelines provide approaches that consider individual factors to inform both strong and conditional recommendations. Conditional recommendations serve as navigational signals for shared decision-making when patient expertise is leveraged to inform individual preferences and values together with clinician expertise in anaphylaxis management to provide patient care bespoke to each patient. As novel approaches to both prevention and treatment of anaphylaxis emerge, an understanding of the significance of strong and conditional recommendations becomes critical to providing individualized and appropriate care for patients at risk for anaphylaxis.

Updated grading system for systemic allergic reactions: Joint Statement of the World Allergy Organization Anaphylaxis Committee and Allergen Immunotherapy Committee

There is a lack of consensus over the description and severity assignment of allergic adverse reactions to immunotherapy, although there seems to be a consensus at least in terms of using the World Allergy Organization (WAO) grading systems to describe local adverse events for Sublingual Immunotherapy (SLIT) and Systemic Allergic Reactions (SARs) to Subcutaneous Immunotherapy (SCIT) amongst the major national/regional allergy societies. In this manuscript, we propose a modification of the previous WAO Grading system for SARs, which aligns with the newly-proposed Consortium for Food Allergy Research (CoFAR) Grading Scale for Systemic Allergic Reactions in Food Allergy (version 3.0). We hope this can facilitate a unified grading system appropriate to SARs due to allergen immunotherapy, independent of allergen and route of administration, and across clinical and research practice.

The bradykinin-forming cascade in anaphylaxis and ACE-inhibitor induced angioedema/airway obstruction

Anaphylaxis is a potentially life-threatening multi-system allergic reaction to a biological trigger resulting in the release of potent inflammatory mediators from mast cells and basophils and causing symptoms in at least two organ systems that generally include skin, lungs, heart, or gastrointestinal tract in any combination. One exception is profound hypotension as an isolated symptom. There are two types of triggers of anaphylaxis: immunologic and non-Immunologic. Immunologic anaphylaxis is initiated when a foreign antigen directly binds to IgE expressed on mast cells or basophils and induces the release of histamine and other inflammatory substances resulting in vasodilation, vascular leakage, decreased peripheral vascular resistance, and heart muscle depression. If left untreated, death by shock (profound hypotension) or asphyxiation (airway obstruction) can occur. The non-immunologic pathway, on the other hand, can be initiated in many ways. A foreign substance can directly bind to receptors of mast cells and basophils leading to degranulation. There can be immune complex activation of the classical complement cascade with the release of anaphylatoxins C3a and C5a with subsequent recruitment of mast cells and basophils. Finally, hyperosmolar contrast agents can cause blood cell lysis, enzyme release, and complement activation, resulting in anaphylactoid (anaphylactic-like) symptoms. In this report we emphasize the recruitment of the bradykinin-forming cascade in mast cell dependent anaphylactic reactions as a potential mediator of severe hypotension, or airway compromise (asthma, laryngeal edema). We also consider airway obstruction due to inhibition of angiotensin converting enzyme with a diminished rate of endogenous bradykinin metabolism, leading not only to laryngeal edema, but massive tongue swelling with aspiration of secretions.