Anaphylaxis: clinical patterns, mediator release, and severity

Adrenaline Auto-Injectors for Preventing Fatal Anaphylaxis

Anaphylaxis affects up to 5% of people during their lifetime. Although anaphylaxis usually resolves without long-term physical consequences, it can result in anxiety and quality of life impairment. Rarely and unpredictably, community anaphylaxis can cause rapid physiological decompensation and death. Adrenaline (epinephrine) is the cornerstone of anaphylaxis treatment, and provision of adrenaline autoinjectors (AAI) has become a standard of care for people at risk of anaphylaxis in the community. In this article, we explore the effectiveness of AAIs for preventing fatal outcomes in anaphylaxis, using information drawn from animal and human in vivo studies and epidemiology. We find that data support the effectiveness of intravenous adrenaline infusions for reversing physiological features of anaphylaxis, typically at doses from 0.05 to 0.5 μg/kg/min for 1-2 h, or ~ 10 μg/kg total dose. Intramuscular injection of doses approximating 10 μg/kg in humans can result in similar peak plasma adrenaline levels to intravenous infusions, at 100-500 pg/mL. However, these levels are typically short-lived following intramuscular adrenaline, and pharmacokinetic and pharmacodynamic outcomes can be unpredictable. Epidemiological data do not support an association between increasing AAI prescriptions and reduced fatal anaphylaxis, although carriage and activation rates remain low. Taken together, these data suggest that current AAIs have little impact on rates of fatal anaphylaxis, perhaps due to a lack of sustained and sufficient plasma adrenaline concentration. Effects of AAI prescription on quality of life may be variable. There is a need to consider alternatives, which can safely deliver a sustained adrenaline infusion via an appropriate route.

Epidemiology, Risk Factors, and Management of Biphasic Anaphylaxis

PURPOSE OF REVIEW

Biphasic anaphylaxis is a variant of anaphylaxis characterized by recurrence of symptoms after initial resolution of anaphylaxis. It was first described in the mid 1990s by Popa and Lerner. Our understanding of the pathophysiology and epidemiology of the condition has advanced considerably since then. The purpose of this manuscript is to review the literature surrounding biphasic anaphylaxis while highlighting key works and recent advances.

RECENT FINDINGS

Prior studies have estimated biphasic anaphylaxis occurs in 0.4-20% of anaphylaxis episodes. The wide range may be related to differences in anaphylaxis diagnostic criteria which was inconsistent across studies. Recently identified risk factors for occurrence of biphasic anaphylaxis include severe initial symptoms including hypotension or hypoxia, delay in epinephrine use, and greater than one dose of epinephrine required to treat symptoms. Despite our progress to better understand biphasic anaphylaxis, there remain gaps in the literature. This article aims to review the recent literature including, epidemiology, risk factors, and management of biphasic anaphylaxis.

10 practical priorities to prevent and manage serious allergic reactions: GA2LEN ANACare and EFA Anaphylaxis Manifesto

This Anaphylaxis Manifesto calls on communities to prioritise 10 practical actions to improve the lives of people at risk of serious allergic reactions. The Global Allergy and Asthma European Network and the European Federation of Allergy and Airways Diseases Patients' Associations (EFA) compiled patient-centric priorities. We used qualitative consensus methods, research evidence and feedback from over 200 patient groups, stakeholder organisations and healthcare professionals. We encourage healthcare, education and food organisations to collaborate with people at risk of serious allergic reactions to tackle safety, anxiety and financial burdens for individuals and societies. Key priorities for prevention include awareness-raising campaigns for the public and professionals, school and workplace initiatives and mandatory precautionary allergen labels on food. Priorities for improving immediate and long-term management include educating healthcare professionals, patients and schools about when and how to use adrenaline, funding two approved adrenaline devices for everyone at risk, and facilitating access to allergy specialists. Integrated care pathways should include clinical and non-clinical management options such as individualised risk assessment and quality of life assessment, self-management plans, dietetic and psychosocial support and peer support. Organisations around the world are committing to work together towards these priorities.

Anaphylaxis: first clinical presentation, subsequent referral practise, and suspected elicitor-an observational study

Anaphylaxis is an allergic manifestation characterised by rapid onset and progression. Rapid treatment may be challenging in patients with atypical symptoms or no previous history of anaphylaxis. This study aimed to describe the clinical prehospital presentation of first-time anaphylactic patients. To help target educational initiatives, we sought to identify which groups of medical professionals are most likely to encounter first-time anaphylactic patients and investigated the referral pattern for suspected anaphylactic patients for specialised treatment. A retrospective register-based study from the Region of Southern Denmark. Patients referred to the Allergy Centre, Odense University Hospital, from 2019 to 2021 were included. The medical records were manually reviewed for first contact with the emergency departments or the emergency medical service. 444 patients with suspected anaphylaxis were referred. 226 patients had grade 3-5 systemic allergic reactions as classified by the World Allergy Organisation; 90% had cutaneous symptoms, 63% symptoms from the central nervous system, 42% gastrointestinal symptoms, 40% cardiovascular symptoms, 36% had upper-airway symptoms, and 36% had lower-airway symptoms. Patients treated prehospitally had a significantly more severe degree of anaphylaxis than patients only treated within the hospital. More than half of the patients with suspected anaphylaxis were referred to the Allergy Centre from the emergency departments. Patients with allergies progressing to severe anaphylaxis most often are treated prehospitally before transport to emergency departments. From the emergency departments, they are referred to the allergy centre. Education concerning the immediate treatment of severe anaphylaxis should primarily be targeted towards prehospital care providers.

Vaping-associated illness: a reassessment

BACKGROUND

In 2019, there was widespread presentation of respiratory distress as well as other organ system involvement in patients with a history of vaping. There continue to be reports of vaping-associated illness (VAI). This has come to be known as e-cigarette and vaping product associated lung injury (EVALI). The mechanism of injury remains unclear.

OBJECTIVES

This study reexamines the clinical characteristics of patients affected by vaping and suggests that lung injury may not be the primary organ dysfunction but be part of a larger systemic illness.

METHODS

This is a retrospective chart review of all patients presenting to one hospital identified as having vaping-associated illness RESULTS: Fourteen patients were identified ranging in age from 15 to 33 years. Patients had a broad range of clinical severity. Respiratory symptoms occurred in 64%, gastrointestinal symptoms in 57%, fever in 78%, neurological symptoms in 15% and other constitutional symptoms in 50%. 35% presented with no respiratory symptoms.

CONCLUSION

While the lungs are certainly involved in vaping-associated illness, recognizing the extent of involvement of other organ systems may provide insight into the pathophysiology of the disease. Providers should be aware that vaping-associated illness presents with a multitude of symptoms outside of lung injury, such as abdominal pain, headache or even fever.

Perioperative anaphylaxis: updates on pathophysiology

PURPOSE OF REVIEW

Perioperative anaphylaxis has historically been attributed to IgE/FcεRI-mediated reactions; there is now recognition of allergic and nonallergic triggers encompassing various reactions beyond IgE-mediated responses. This review aims to present recent advancements in knowledge regarding the mechanisms and pathophysiology of perioperative anaphylaxis.

RECENT FINDINGS

Emerging evidence highlights the role of the mast-cell related G-coupled protein receptor X2 pathway in direct mast cell degranulation, shedding light on previously unknown mechanisms. This pathway, alongside traditional IgE/FcεRI-mediated reactions, contributes to the complex nature of anaphylactic reactions. Investigations into the microbiota-anaphylaxis connection are ongoing, with potential implications for future treatment strategies. While serum tryptase levels serve as mast cell activation indicators, identifying triggers remains challenging. A range of mediators have been associated with anaphylaxis, including vasoactive peptides, proteases, lipid molecules, cytokines, chemokines, interleukins, complement components, and coagulation factors.

SUMMARY

Further understanding of clinical endotypes and the microenvironment where anaphylactic reactions unfold is essential for standardizing mediator testing and characterization in perioperative anaphylaxis. Ongoing research aims to elucidate the mechanisms, pathways, and mediators involved across multiple organ systems, including the cardiovascular, respiratory, and integumentary systems, which will be crucial for improving patient outcomes.

Management of Refractory Anaphylaxis: An Overview of Current Guidelines

In this review, we compare different refractory anaphylaxis (RA) management guidelines focusing on cardiovascular involvement and best practice recommendations, discuss postulated pathogenic mechanisms underlining RA and highlight knowledge gaps and research priorities. There is a paucity of data supporting existing management guidelines. Therapeutic recommendations include the need for the timely administration of appropriate doses of aggressive fluid resuscitation and intravenous (IV) adrenaline in RA. The preferred second-line vasopressor (noradrenaline, vasopressin, metaraminol and dopamine) is unknown. Most guidelines recommend IV glucagon for patients on beta-blockers, despite a lack of evidence. The use of methylene blue or extracorporeal life support (ECLS) is also suggested as rescue therapy. Despite recent advances in understanding the pathogenesis of anaphylaxis, the factors that lead to a lack of response to the initial adrenaline and thus RA are unclear. Genetic factors, such as deficiency in platelet activating factor-acetyl hydrolase or hereditary alpha-tryptasaemia, mastocytosis may modulate reaction severity or response to treatment. Further research into the underlying pathophysiology of RA may help define potential new therapeutic approaches and reduce the morbidity and mortality of anaphylaxis.

Disseminated Intravascular Coagulation in Anaphylaxis

Anaphylaxis is a life-threatening condition that involves severe cutaneous, respiratory, and cardiovascular symptoms. Disseminated intravascular coagulation (DIC) is an acquired, widespread activation of coagulation that can be caused by infectious conditions (e.g., sepsis) and noninfectious conditions. The onset of DIC following anaphylaxis is not commonly known, and information regarding the pathomechanism linking anaphylaxis to DIC is scarce. Further, demographic and clinical data in anaphylaxis-induced DIC are still missing to this day. Triggered by a case of anaphylaxis-induced DIC that seamlessly transitioned to lethal sepsis-induced DIC, we aimed to characterize the patient population affected by anaphylaxis-induced DIC by performing a review of existing literature and expand the discussion to underlying mechanisms. The overall mortality of the patient cohort (n = 30) identified by the literature review was 50%. All patients that died either suffered a bleeding event or a thrombotic event. The majority of patients (n = 25/30; 83%) had bleeding events; thrombotic events were only reported in nonsurvivors (n = 9/15 or 60% of nonsurvivors; vs. n = 0/15 in survivors; p < 0.001). Nonsurvivors of anaphylaxis-induced DIC were on average 25 years older than survivors (p = 0.068). In conclusion, DIC can complicate anaphylaxis and is expected to contribute to poor microvascular perfusion after anaphylaxis. Particularly, elderly patients with known cardiovascular disease and patients who develop thrombotic events are susceptible to lethal outcomes. As a rare and largely uncharacterized disease entity, further research is needed to investigate the link between DIC and anaphylaxis and to potentially identify better treatment strategies.

Anaphylaxis in a Swiss university emergency department: clinical characteristics and supposed triggers

BACKGROUND

Anaphylaxis is the most severe form of acute systemic and potentially life-threatening reactions triggered by mast and basophilic cells. Recent studies show a worldwide incidence between 50 and 112 occurrences per 100,000 person-years. The most identified triggers are food, medications, and insect venoms. We aimed to analyze triggers and clinical symptoms of patients presenting to a Swiss university emergency department for adults.

METHODS

Six-year retrospective analysis (01/2013 to 12/2018) of all patients (> 16 years of age) admitted with moderate or severe anaphylaxis (classification of Ring and Messmer ≥ 2) to the emergency department. Patient and clinical data were extracted from the electronic medical database of the emergency department.

RESULTS

Of the 531 includes patients, 53.3% were female, the median age was 38 [IQR 26-51] years. The most common suspected triggers were medications (31.8%), food (25.6%), and insect stings (17.1%). Organ manifestations varied among the different suspected triggers: for medications, 90.5% of the patients had skin symptoms, followed by respiratory (62.7%), cardiovascular (44.4%) and gastrointestinal symptoms (33.7%); for food, gastrointestinal symptoms (39.7%) were more frequent than cardiovascular symptoms (36.8%) and for insect stings cardiovascular symptoms were apparent in 63.8% of the cases.

CONCLUSIONS

Average annual incidence of moderate to severe anaphylaxis during the 6-year period in subjects > 16 years of age was 10.67 per 100,000 inhabitants. Medications (antibiotics, NSAID and radiocontrast agents) were the most frequently suspected triggers. Anaphylaxis due to insect stings was more frequently than in other studies. Regarding clinical symptoms, gastrointestinal symptoms need to be better considered, especially that initial treatment with epinephrine is not delayed.

Helper T cell subsets: Development, function and clinical role in hypersensitivity reactions in the modern perspective

Helper T cells are traditionally classified into T helper 1 (TH1) and T helper 2 (TH2). The more recent discoveries of T helper 17 (TH17), follicular helper T cells (TFH) and regulatory T cells (Treg) enhanced our understanding on the mechanisms of immune function and hypersensitivity reactions, which shaped the modern perspective on the function and role of these different subsets of helper T cells in hypersensitivity reactions. Each subset of helper T cells has characteristic roles in different types of hypersensitivity reactions, hence giving rise to the respective characteristic clinical manifestations. The roles of helper T cells in allergic contact dermatitis (TH1-mediated), drug rash with eosinophilia and systemic symptoms (DRESS) syndrome (TH2-mediated), and acute generalised exanthematous pustulosis (AGEP) (TH17-mediated) are summarised in this article, demonstrating the correlation between the type of helper T cell involved and the clinical features. TFH plays crucial roles in antibody class-switch recombination; they may be implicated in antibody-mediated hypersensitivity reactions, but further research is warranted to delineate their exact pathogenic roles. The helper T cell subsets and their specific cytokine profiles implicated in different hypersensitivity reactions could be potential treatment targets by biologics, but more clinical trials are warranted to establish their clinical effectiveness.

Combined transcriptomics and TMT-proteomics reveal abnormal complement and coagulation cascades in cow's milk protein allergy

Cow's milk protein allergy (CMPA) is primarily due to the inability of the intestinal mucosa to establish typical immunological tolerance to proteins found in cow's milk, and the specific molecular mechanism is still unclear. In order to investigate molecular alterations in intestinal tissues during CMPA occurrence, this study analyzed the jejunal tissue of β-lactoglobulin (BLG)-sensitized mice through transcriptomics and quantitative tandem mass tag (TMT)-labeled proteomics. A total of 475 differentially expressed genes (256 up-regulated, 219 down-regulated) and 94 differentially expressed proteins (65 up-regulated, 29 down-regulated) were identified. Comparing the KEGG pathways of the two groups, it was found that both were markedly enriched in the signaling pathways of complement and coagulation cascade. Among these, kallikrein B1 (KLKB1) in this pathway is speculated to be pivotal in CMPA. It may potentially enhance the release of bradykinin by activating the kallikrein-kinin system, leading to pro-inflammatory effects and exacerbating intestinal mucosal damage. This study suggests that the pathways of complement and coagulation cascades could be significant in the context of intestinal immunity in CMPA, and KLKB1 may be its potential therapeutic target.

Protective role of protease-activated receptor-2 in anaphylaxis model mice

Anaphylaxis is a severe life-threatening hypersensitivity reaction induced by mast cell degranulation. Among the various mediators of mast cells, little is known about the role of tryptase. Therefore, we aimed to elucidate the role of protease-activating receptor-2 (PAR-2), a receptor activated by tryptase, in murine anaphylactic models using PAR-2-deficient mice and newly generated tryptase-deficient mice. Anaphylaxis was induced by IgE-dependent and IgE-independent mast cell degranulation in mice. PAR-2 deficiency exacerbated the decrease in body temperature and hypotension during anaphylaxis; however, the number of skin mast cells, degree of mast cell degranulation, and systemic and local vascular hyperpermeability were comparable in PAR-2 knockout and wild-type mice. Nitric oxide, which is produced by endothelial nitric oxide synthase (eNOS), is an indispensable vasodilator in anaphylaxis. In the lungs of anaphylactic mice, PAR-2 deficiency promoted eNOS expression and phosphorylation, suggesting a protective effect of PAR-2 against anaphylaxis by downregulating eNOS activation and expression. Based on the hypothesis that the ligand for PAR-2 in anaphylaxis is mast cell tryptase, tryptase-deficient mice were generated using CRISPR-Cas9. In wild-type mice, the PAR-2 antagonist exacerbated the body temperature drop due to anaphylaxis; however, the effect of the PAR-2 antagonist was abolished in tryptase-deficient mice. These results suggest that tryptase is a possible ligand of PAR-2 in anaphylaxis and that the tryptase/PAR-2 pathway attenuates the anaphylactic response in mice.

A retrospective audit of adult and paediatric anaphylaxis management from two Australian metropolitan mixed emergency departments

BACKGROUND

Anaphylaxis is a potentially life-threatening allergic reaction, with presentations to emergency departments (EDs) increasing across Australia. Understanding the features of those presenting with anaphylaxis and aspects related to its optimal clinical management across the admission, treatment and discharge settings is needed to minimise its impact. We aimed to evaluate the nature and management of presentations related to anaphylaxis across two Australian EDs.

METHODS

Retrospective audit of paediatric and adult patients presenting to a community or tertiary level ED with anaphylaxis from 1 May 2018 to 30 April 2019. Data extracted from medical records included demographic characteristics, causative agents, clinical features, treatments administered across community, ambulance or ED settings, as well as post-discharge care arrangements including provision of Adrenaline Auto-Injector (AAI) and Allergy/Anaphylaxis Action Plan (AAP).

RESULTS

A total of 369 (107 paediatric and 262 adult) ED presentations were identified. A total of 94 (36%) adult and 46 (43%) paediatric patients received pre-hospital adrenaline, with a further 91 (35%) adult and 29 (27%) paediatric patients receiving a dose of adrenaline in the ED. The most commonly administered treatment in ED were corticosteroids, given to 157 (60%) adult and 55 (51%) paediatric patients. Among those requiring an AAI for discharge, 123/210 (59%) adult and 57/91 (63%) of paediatric patients left hospital with an AAI. In contrast, among those requiring an allergy/anaphylaxis action plan (AAP) on discharge, 61/206 (30%) adult and 30/90 (33%) of paediatric patients left hospital with one. Factors associated with an increased likelihood of receiving AAI on discharge in paediatric and adult patients included receipt of any adrenaline, receipt of two or more doses of adrenaline, and longer duration of hospital stay. Adults presenting within business hours were more likely to be discharged with AAI, but no such difference was observed for paediatric patients. Similar findings were evident for provision of AAP on discharge.

CONCLUSION

These findings demonstrate the need to improve assessment and treatment in the ED. In particular, the observed large variability in provision of AAI and AAP on discharge presents opportunities to explore strategies to improve awareness and provision of these critical components of post-discharge care.

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.

Anaphylaxis: A 2023 practice parameter update

This practice parameter update focuses on 7 areas in which there are new evidence and new recommendations. Diagnostic criteria for anaphylaxis have been revised, and patterns of anaphylaxis are defined. Measurement of serum tryptase is important for diagnosis of anaphylaxis and to identify underlying mast cell disorders. In infants and toddlers, age-specific symptoms may differ from older children and adults, patient age is not correlated with reaction severity, and anaphylaxis is unlikely to be the initial reaction to an allergen on first exposure. Different community settings for anaphylaxis require specific measures for prevention and treatment of anaphylaxis. Optimal prescribing and use of epinephrine autoinjector devices require specific counseling and training of patients and caregivers, including when and how to administer the epinephrine autoinjector and whether and when to call 911. If epinephrine is used promptly, immediate activation of emergency medical services may not be required if the patient experiences a prompt, complete, and durable response. For most medical indications, the risk of stopping or changing beta-blocker or angiotensin-converting enzyme inhibitor medication may exceed the risk of more severe anaphylaxis if the medication is continued, especially in patients with insect sting anaphylaxis. Evaluation for mastocytosis, including a bone marrow biopsy, should be considered for adult patients with severe insect sting anaphylaxis or recurrent idiopathic anaphylaxis. After perioperative anaphylaxis, repeat anesthesia may proceed in the context of shared decision-making and based on the history and results of diagnostic evaluation with skin tests or in vitro tests when available, and supervised challenge when necessary.

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.

Fatal and Near-Fatal Anaphylaxis: Data From the European Anaphylaxis Registry and National Health Statistics

BACKGROUND

Anaphylaxis is a serious systemic reaction-data on fatal and near-fatal reactions are limited.

OBJECTIVE

To better understand clinical patterns and risks factors of severe anaphylaxis by a deep analysis of data from fatal and near-fatal anaphylaxis.

METHODS

Data from the European Anaphylaxis Registry on fatal/near-fatal anaphylactic reactions and national data on anaphylaxis fatalities were investigated.

RESULTS

A total of 305 fatal/near-fatal reactions among children and adults including 35 fatalities from the European Anaphylaxis Registry were identified. The most frequent elicitors were drugs, insects, and food. Male patients (66%/60%) were more frequently affected. Male sex, higher age, concomitant mastocytosis, and cardiovascular disease were associated with a more severe outcome. With increasing reaction severity, skin symptoms were less frequently observed (45% of fatal reactions). In parallel, anaphylaxis mortality rates were studied. The data show that anaphylaxis mortality rates increased in Germany from 0.48 (2009) to 0.59 per 1,000,000 population per year (2020). This increase was apparent only in the female population. In this data set, drugs were the most frequent elicitor of anaphylaxis fatalities, and the rate for this increased over time.

CONCLUSIONS

We identified not only elicitors but also individual factors to be associated with an increased risk of fatal anaphylaxis. Such patients should be recognized and managed with great caution. The increase in drug-induced fatalities points to the need for a better allergological care of patients suffering from drug hypersensitivity.

Fatal ampicillin-sulbactam anaphylaxis in a 34-year-old male

A 34-year-old man receiving his first dose of ampicillin-sulbactam for osteomyelitis in a hospital setting experienced fatal drug-induced anaphylaxis.

Complement-mediated immune mechanisms in allergy

Allergic conditions are associated with canonical and noncanonical activation of the complement system leading to the release of several bioactive mediators with inflammatory and immunoregulatory properties that regulate the immune response in response to allergens during the sensitization and/or the effector phase of allergic diseases. Further, immune sensors of complement and regulator proteins of the cascade impact on the development of allergies. These bioactive mediators comprise the small and large cleavage fragments of C3 and C5. Here, we provide an update on the multiple roles of immune sensors, regulators, and bioactive mediators of complement in allergic airway diseases, food allergies, and anaphylaxis. A particular emphasis is on the anaphylatoxins C3a and C5a and their receptors, which are expressed on many of the effector cells in allergy such as mast cells, eosinophils, basophils, macrophages, and neutrophils. Also, we will discuss the multiple pathways, by which the anaphylatoxins initiate and control the development of maladaptive type 2 immunity including their impact on innate lymphoid cell recruitment and activation. Finally, we briefly comment on the potential to therapeutically target the complement system in different allergic conditions.

Retrospective evaluation of hypersensitivity reactions and anaphylaxis in dogs (2003-2014): 86 cases

OBJECTIVE

To characterize anaphylactic reactions in dogs, including clinical signs, severity, treatments, prognosis, and estimated incidence. To determine whether glucocorticoids influence clinical recovery and survival.

DESIGN

Retrospective study between January 1, 2003 and April 28, 2014.

SETTING

University teaching hospital.

ANIMALS

Eighty-six dogs treated for a type I hypersensitivity reaction. Nineteen dogs fulfilled the criteria for anaphylaxis, and 67 dogs had mild cutaneous reactions.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The estimated incidence was 0.04% for anaphylaxis and 0.15% for mild hypersensitivity reactions. The female:male ratio (2.3:1) was significantly higher (P = 0.032) compared to our source population (ratio of 1:1.158). Vaccines were the most frequent trigger for anaphylaxis (57.9%) and mild hypersensitivity reactions (28.4%). Seventy-four (86%) dogs had cutaneous signs, and 11 (57.9%) dogs with anaphylaxis had no cutaneous signs reported. Forty-two (48.8%) dogs received both an H1 antagonist and a glucocorticoid, 34 (39.5%) dogs received an H1 antagonist only, and 6 (6.9%) dogs received a glucocorticoid only. The majority of the dogs survived, and 1 was euthanized due to complications. Clinical signs associated with nonsurvival included respiratory signs (P = 0.006), particularly respiratory distress (P < 0.00001) and cyanosis (P < 0.00001), and circulatory shock (P = 0.005). The analysis of the interaction between etiology, clinical signs, treatment, and outcome did not show any association between pairs of variables.

CONCLUSIONS

In the current study, anaphylaxis had a relatively good prognosis, and cutaneous signs were not always present. Based on the present data, the use of glucocorticoids to treat mild type I hypersensitivity reactions and anaphylaxis in dogs was not associated with clinical improvement or survival.

Mast Cells and Basophils in IgE-Independent Anaphylaxis

Anaphylaxis is a life-threatening or even fatal systemic hypersensitivity reaction. The incidence of anaphylaxis has risen at an alarming rate in the past decades in the majority of countries. Generally, the most common causes of severe or fatal anaphylaxis are medication, foods and Hymenoptera venoms. Anaphylactic reactions are characterized by the activation of mast cells and basophils and the release of mediators. These cells express a variety of receptors that enable them to respond to a wide range of stimulants. Most studies of anaphylaxis focus on IgE-dependent reactions. The mast cell has long been regarded as the main effector cell involved in IgE-mediated anaphylaxis. This paper reviews IgE-independent anaphylaxis, with special emphasis on mast cells, basophils, anaphylactic mediators, risk factors, triggers, and management.

Contextual community epinephrine prescribing: Is more always better?

OBJECTIVE

Prompt administration of epinephrine is first-line management of anaphylaxis. Although severe anaphylaxis may require more than 1 epinephrine dose, multiple epinephrine device packs may not be necessary for all patients at risk for allergic reactions.

DATA SOURCES

A narrative review was used to describe key considerations to contextualize community epinephrine prescribing.

RESULTS

Anaphylaxis has a lifetime prevalence of 1.6% to 5.1%. Meeting diagnostic criteria for anaphylaxis is not required for epinephrine treatment of a severe allergic reaction. A "1-2-3" approach to anaphylaxis treatment is important to clearly relay central management steps: promptly administer a first dose of intramuscular epinephrine with proper positioning, and activate emergency medical services if immediate symptom resolution does not occur; consider a second dose of intramuscular epinephrine with consideration of oxygen administration and intravenous fluid if initial epinephrine response is not adequate; and consider a third intramuscular epinephrine dose together with consideration of intravenous fluid support and oxygen for continued lack of appropriate response. Although multiple epinephrine doses may be required to treat severe anaphylaxis, 90% of anaphylaxis cases do not require more than 1 epinephrine dose. A universal requirement for multiple epinephrine devices in patients without a history of anaphylaxis is not cost-effective. Patients without a history of anaphylaxis may be managed without multiple device prescriptions within a patient-preference sensitive paradigm of care.

CONCLUSION

Anaphylaxis prevention involves appropriate education to avoid allergen triggers, recognize symptoms of an allergic reaction, rapidly access and administer intramuscular epinephrine, and appropriately activate emergency medical services when needed. For patients with previous anaphylaxis, particularly those who have required more than 1 dose of epinephrine to treat an allergic reaction, possessing multiple epinephrine devices is an important part of managing community anaphylaxis risk.

Overview of Allergy and Anaphylaxis

Allergic reactions and anaphylaxis occur on a severity continuum from mild and self-limited to potentially life-threatening or fatal reactions. Anaphylaxis is typically a multiorgan phenomenon involving a broad range of effector cells and mediators. Emergency department visits for anaphylaxis are increasing, especially among children. There is a broad differential diagnosis for anaphylaxis, and the diagnosis of anaphylaxis can be aided by the use of the National Institutes of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network clinical diagnostic criteria. Risk factors for severe anaphylaxis include older age, delayed epinephrine administration, and cardiopulmonary comorbidities.

[Distributive shock]

In shock there is a significant mismatch between oxygen supply and consumption. In recent years the classification of forms of shock has been established based on pathophysiological and clinical aspects. The term distributive shock includes septic, anaphylactic and neurogenic shock. All these forms share a distinct vasoplegia with a relative volume deficiency. The adequate treatment of patients with distributive shock includes a rapid diagnosis and a consistent emergency treatment consisting of volume and catecholamine administration as well as additional specific emergency procedures when necessary.

Refractory Anaphylaxis: A New Entity for Severe Anaphylaxis

Anaphylaxis reactions lie on a spectrum of severity, ranging from relatively mild lower respiratory involvement (depending on the definition of anaphylaxis used) to more severe reactions that are refractory to initial treatment with epinephrine and may rarely cause death. A variety of grading scales exist to characterize severe reactions, but there is a lack of consensus about the optimal approach to define severity. More recently, a new entity called refractory anaphylaxis (RA) has emerged in the literature, characterized by the persistence of anaphylaxis despite initial epinephrine treatment. However, slightly different definitions have been proposed to date. In this Rostrum, we review these definitions as well as data relating to epidemiology, elicitors, risk factors, and management of RA. We propose a need to align the different definitions for RA, to improve epidemiological surveillance, advance our understanding of the pathophysiology of RA, and optimize management strategies to reduce morbidity and mortality.

Venom Anaphylaxis: Decision Points for a More Aggressive Workup

Diagnostic testing of patients who present for evaluation of insect venom allergy can involve many levels of investigation. A detailed initial history is critical for diagnosis and prognosis. The severity of previous sting reactions and the presence or absence of urticaria or hypotension predict severe future sting reactions and underlying mast cell disorders. Venom skin tests and specific IgE measurement can confirm the diagnosis but have limited positive predictive value for the frequency and severity of future sting reactions. Testing for serum IgE to recombinant venom component allergens can distinguish true allergy from cross-reactivity to honey bee and yellowjacket venoms. Basophil activation tests can improve the detection of venom allergy and predict the severity of reactions and the efficacy of venom immunotherapy but are limited in availability. An elevated basal serum tryptase level is an important marker for severe sting anaphylaxis and underlying mast cell disorders (eg, hereditary α-tryptasemia and clonal mast cell disease). When there is high suspicion (eg, using the Red Espanola de Mastocytosis score), bone marrow biopsy is the definitive tool to characterize mast cell disorders that are associated with the most severe outcomes in patients with insect sting allergy.

IgE-mediated cow's milk allergy in Brazilian children: Outcomes of oral food challenge

Background

Oral food challenge (OFC) is useful for diagnosing food allergies and assessing tolerance, but severe reactions may occur during the procedure.

Objective

To characterize the frequency and severity of reactions during cow's milk (CM) OFCs.

Methods

A cross-sectional study was conducted to analyze the outcome of cow's milk oral food challenges (CMOFCs) performed to confirm IgE-mediated CM allergy or to assess food tolerance. CM was given first as baked milk (BM), followed by whole CM if there was no prior reaction to BM. An OFC was considered positive if IgE-mediated symptoms developed up to 2 h after ingestion. Symptoms were described and variables including age at OFC, prior anaphylaxis, other atopic diseases, and skin test results were compared according to the OFC outcomes.

Results

A total of 266 CMOFCs were performed, including 159 patients with a median age of 6.3 years old. One hundred thirty-six tests were positive and 62 resulted in anaphylaxis. Thirty-nine anaphylactic reactions were observed up to 30 min after the first dose. Severe anaphylaxis (cardiovascular and/or neurological involvement) was reported in 5 tests. A second dose of epinephrine was required in 3 tests, and 1 presented a biphasic response. Younger patients had a higher risk of anaphylaxis during baked milk oral food challenge (BMOFC) (p = 0.009). The frequency of anaphylaxis was higher in patients submitted to BM (p = 0.009).

Conclusions

Anaphylaxis is a known complication of CMOFCs even when there is no prior anaphylaxis or when conducted with baked products. This study reinforces the importance of conducting OFC in appropriate settings with a well-trained team.

Rituximab-Induced Serum Sickness Overlapping With Anaphylaxis: A Case Report

Serum sickness (SS) and anaphylaxis are well-documented complications of rituximab (RTX) infusions. While the first presents usually as a triad of fever, rash, and arthralgias occurring seven to 14 days after infusion, the second presents as a sudden onset of hemodynamic instability, bronchospasm, and a pruritic erythematous rash, occurring within the first few hours after infusion. We present here a case of serum sickness associated with anaphylaxis five days after the first infusion of a second course of RTX. Only eight cases of rituximab-induced serum sickness (RISS) associated with hemodynamic instability have been reported. We describe the first case of proven anaphylaxis with an elevated tryptase serum level occurring in conjunction with RISS, six days after a third RTX infusion.

Peanut allergen inhibition prevents anaphylaxis in a humanized mouse model

Peanut-induced allergy is an immunoglobulin E (IgE)-mediated type I hypersensitivity reaction that manifests symptoms ranging from local edema to life-threatening anaphylaxis. Although there are treatments for symptoms in patients with allergies resulting from allergen exposure, there are few preventive therapies other than strict dietary avoidance or oral immunotherapy, neither of which are successful in all patients. We have previously designed a covalent heterobivalent inhibitor (cHBI) that binds in an allergen-specific manner as a preventive for allergic reactions. Building on previous in vitro testing, here, we developed a humanized mouse model to test cHBI efficacy in vivo. Nonobese diabetic-severe combined immunodeficient γc-deficient mice expressing transgenes for human stem cell factor, granulocyte-macrophage colony-stimulating factor, and interleukin-3 developed mature functional human mast cells in multiple tissues and displayed robust anaphylactic reactions when passively sensitized with patient-derived IgE monoclonal antibodies specific for peanut Arachis hypogaea 2 (Ara h 2). The allergic response in humanized mice was IgE dose dependent and was mediated by human mast cells. Using this humanized mouse model, we showed that cHBI prevented allergic reactions for more than 2 weeks when administered before allergen exposure. cHBI also prevented fatal anaphylaxis and attenuated allergic reactions when administered shortly after the onset of symptoms. cHBI impaired mast cell degranulation in vivo in an allergen-specific manner. cHBI rescued the mice from lethal anaphylactic responses during oral Ara h 2 allergen-induced anaphylaxis. Together, these findings suggest that cHBI has the potential to be an effective preventative for peanut-specific allergic responses in patients.

Feasibility of detecting snake envenomation biomarkers from dried blood spots

Biofluid proteomics is a sensitive and high throughput technique that provides vast amounts of molecular data for biomarker discovery. More recently, dried blood spots (DBS) have gained traction as a stable, noninvasive, and relatively cheap source of proteomic data for biomarker identification in disease and injury. Snake envenomation is responsible for significant morbidity and mortality worldwide; however, much remains unknown about the systemic molecular response to envenomation and acquiring biological samples for analysis is a major hurdle. In this study, we utilized DBS acquired from a case of lethal rattlesnake envenomation to determine the feasibility of discovering biomarkers associated with human envenomation. We identified proteins that were either unique or upregulated in envenomated blood compared to non-envenomated blood and evaluated if physiological response pathways and protein markers that correspond to the observed syndromes triggered by envenomation could be detected. We demonstrate that DBS provide useful proteomic information on the systemic processes that resulted from envenomation in this case and find evidence for a massive and systemic inflammatory cascade, combined with coagulation dysregulation, complement system activation, hypoxia response activation, and apoptosis. We also detected potential markers indicative of lethal anaphylaxis, cardiac arrest, and brain death. Ultimately, DBS proteomics has the potential to provide stable and sensitive molecular data on envenomation syndromes and response pathways, which is particularly relevant in low-resource areas which may lack the materials for biofluid processing and storage.

Integrative transcriptomic analysis in human and mouse model of anaphylaxis identifies gene signatures associated with cell movement, migration and neuroinflammatory signalling

Background

Anaphylaxis is an acute life-threatening allergic reaction and a concern at a global level; therefore, further progress in understanding the underlying mechanisms and more effective strategies for diagnosis, prevention and management are needed.

Objective

We sought to identify the global architecture of blood transcriptomic features of anaphylaxis by integrating expression data from human patients and mouse model of anaphylaxis.

Methods

Bulk RNA-sequencings of peripheral whole blood were performed in: i) 14 emergency department (ED) patients with acute anaphylaxis, predominantly to Hymenoptera venom, ii) 11 patients with peanut allergy undergoing double-blind, placebo-controlled food challenge (DBPCFC) to peanut, iii) murine model of IgE-mediated anaphylaxis. Integrative characterisation of differential gene expression, immune cell-type-specific gene expression profiles, and functional and pathway analysis was undertaken.

Results

1023 genes were commonly and significantly dysregulated during anaphylaxis in ED and DBPCFC patients; of those genes, 29 were also dysregulated in the mouse model. Cell-type-specific gene expression profiles showed a rapid downregulation of blood basophil and upregulation of neutrophil signature in ED and DBPCFC patients and the mouse model, but no consistent and/or significant differences were found for other blood cells. Functional and pathway analysis demonstrated that human and mouse blood transcriptomic signatures of anaphylaxis follow trajectories of upregulation of cell movement, migration and neuroinflammatory signalling, and downregulation of lipid activating nuclear receptors signalling.

Conclusion

Our study highlights the matched and extensive blood transcriptomic changes and suggests the involvement of discrete cellular components and upregulation of migration and neuroinflammatory pathways during anaphylaxis.

Anaphylaxis in elderly people

PURPOSE OF REVIEW

Anaphylaxis is common in old-age adults but is insufficiently understood by physicians, and may be underdiagnosed. This review discusses the specificities of anaphylaxis in this age group and stresses the importance of adrenaline in its management.

RECENT FINDINGS

Data from the European Anaphylaxis Registry on elderly patients is a major finding. Other findings include the prevention of possible anaphylactic reactions in coronavirus disease 2019 vaccination as well as some new epidemiologic data.

SUMMARY

The most common risk factors are hymenoptera venom and food and drug allergy. Cardiovascular symptoms are the most important ones to reverse in old-age adults, especially due to the multiple comorbidities. Anaphylaxis in old-age adults has a more severe outcome than in younger ones. Polypharmacy is a specific factor to be considered. The Airway, Breathing, Circulation, Disability, Exposure (ABCDE) algorithm is applicable in all clinical emergencies for immediate assessment and treatment, and should be considered for all patients. Adrenaline is the mainstay of the management of the condition. There are no absolute contraindications to the prescription of self-injectable adrenaline in elderly individuals at risk of anaphylaxis.

Canadian Anaphylaxis Network-Predicting Recurrence after Emergency Presentation for Allergic REaction (CAN-PREPARE): a prospective, cohort study protocol

INTRODUCTION

Anaphylaxis is a severe, potentially fatal multiorgan system manifestation of an allergic reaction. The highest incidence of anaphylaxis is in children and adolescents. Biphasic anaphylaxis (BA) is defined as the recurrence of allergic symptoms after resolution of an initial reaction. It has been reported to occur in 10%-20% of cases within 1-48 hours from the onset of the initial reaction. The dilemma for physicians is determining which patients with resolved anaphylaxis should be observed for BA and for how long. Guidelines for duration of postanaphylaxis monitoring vary, are based on limited evidence and can have unintended negative impacts on patient safety, quality of life and healthcare resources. The objectives of this study are to derive a prognostic model for BA and to develop a risk-scoring system that informs disposition decisions of children who present to emergency departments (ED) with anaphylaxis.

METHODS AND ANALYSIS

This prospective multicentre cohort study will enrol 1682 patients from seven paediatric EDs that are members of the Paediatric Emergency Research Canada network. We will enrol patients younger than 18 years of age with an allergic reaction meeting anaphylaxis diagnostic criteria. Trained ED research assistants will screen, obtain consent and prospectively collect study data. Research assistants will follow patients during their ED visit and ascertain, in conjunction with the medical team, if the patient develops BA. A standardised follow-up survey conducted following study enrolment will determine if a biphasic reaction occurred after ED disposition. Model development will conform to the broad principles of the PROGRESS (Prognosis Research Strategy) framework and reporting will follow the Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis Statement.

ETHICS AND DISSEMINATION

Ethics approval has been received from all participating centres. Our dissemination plan focuses on informing clinicians, policy makers and parents of the results through publication in peer-reviewed journals and broadcasting on multiple media platforms.

TRIAL REGISTRATION NUMBER

NCT05135377.

Combined Treatment with KV Channel Inhibitor 4-Aminopyridine and either γ-Cystathionine Lyase Inhibitor β-Cyanoalanine or Epinephrine Restores Blood Pressure, and Improves Survival in the Wistar Rat Model of Anaphylactic Shock

Simple Summary

Allergic diseases are presenting a constant increase all over the world and caused by such different substances as food, drugs, and pollens. Anaphylactic shock is the more severe complication of allergy which can induce death if the treatment is not administered immediately. Some patients do not respond to the recommended treatment, intra venous or intramuscular epinephrine. The pathophysiology of anaphylactic shock is still under investigation. The mediators released after the activation of mast cells and basophiles act on endothelial cells and smooth muscle cells, inducing the vasodilation responsible for hypotension and shock. Nitric oxide and hydrogen sulphide are both intracellular mediators that induce vasodilation. The role of potassium voltage dependent channels is suspected. We aimed to demonstrate the ability of a blocker of potassium voltage dependent channels, 4-aminopyridine, alone or in combination with inhibitors of cystathionine γ-lyase to restore blood pressure and improve survival in an ovalbumin rat anaphylactic shock model. The blockade of potassium voltage dependent channels alone or combined with inhibitors of cystathionine γ-lyase, dl-propargylglycine, or β-cyanoalanine restored blood pressure and improved survival. These findings suggest possible investigative treatment pathways for research concerning epinephrine-refractory anaphylactic shock in patients.

Abstract

The mechanism of anaphylactic shock (AS) remains incompletely understood. The potassium channel blocker 4-aminopyridine (4-AP), the inhibitors of cystathionine γ-lyase (ICSE), dl-propargylglycine (DPG) or β-cyanoalanine (BCA), and the nitric oxide (NO) synthase produce vasoconstriction and could be an alternative for the treatment of AS. The aim of this study was to demonstrate the ability of L-NAME, ICSE alone or in combination with 4-AP to restore blood pressure (BP) and improve survival in ovalbumin (OVA) rats AS. Experimental groups included non-sensitized Wistar rats (n = 6); AS (n = 6); AS (n = 10 per group) treated i.v. with 4-AP (AS+4-AP), epinephrine (AS+EPI), AS+DPG, AS+BCA, or with L-NAME (AS+L-NAME); or AS treated with drug combinations 4-AP+DPG, 4-AP+BCA, 4-AP+L-NAME, or 4-AP+EPI. AS was induced by i.v. OVA (1 mg). Treatments were administered i.v. one minute after AS induction. Mean arterial BP (MAP), heart rate (HR), and survival were monitored for 60 min. Plasma levels of histamine, prostaglandin E2 (PGE2) and F2 (PGF2α), leukotriene B4 and C4, angiotensin II, vasopressin, oxidative stress markers, pH, HCO3, PaO2, PaCO2, and K+ were measured. OVA induced severe hypotension and all AS rats died. Moreover, 4-AP, 4-AP+EPI, or 4-AP+BCA normalized both MAP and HR and increased survival. All sensitized rats treated with 4-AP alone or with 4-AP+BCA survived. The time-integrated MAP “area under the curve” was significantly higher after combined 4-AP treatment with ICSE. Metabolic acidosis was not rescued and NO, ICSE, and Kv inhibitors differentially alter oxidative stress and plasma levels of anaphylactic mediators. The AS-induced reduction of serum angiotensin II levels was prevented by 4-AP treatment alone or in combination with other drugs. Further, 4-AP treatment combined with EPI or with BCA also increased serum PGF2α, whereas only the 4-AP+EPI combination increased serum LTB4. Serum vasopressin and angiotensin II levels were increased by 4-AP treatment alone or in combination with other drugs. Moreover, 4-AP alone and in combination with inhibition of cystathionine γ-lyase or EPI normalizes BP, increases serum vasoconstrictor levels, and improves survival in the Wistar rat model of AS. These findings suggest possible investigative treatment pathways for research into epinephrine-refractory anaphylactic shock in patients.

IgG Subclass-Dependent Pulmonary Antigen Retention during Acute IgG-Dependent Systemic Anaphylaxis in Mice

Mouse models of active systemic anaphylaxis rely predominantly on IgG Abs forming IgG–allergen immune complexes that induce IgG receptor–expressing neutrophils and monocytes/macrophages to release potent mediators, leading to systemic effects. Whether anaphylaxis initiates locally or systemically remains unknown. In this study, we aimed at identifying the anatomical location of IgG–allergen immune complexes during anaphylaxis. Active systemic anaphylaxis was induced following immunization with BSA and i.v. challenge with fluorescently labeled BSA. Ag retention across different organs was examined using whole-body fluorescence imaging, comparing immunized and naive animals. Various mouse models and in vivo deletion strategies were employed to determine the contribution of IgG receptors, complement component C1q, myeloid cell types, and anaphylaxis mediators. We found that following challenge, Ag diffused systemically, but specifically accumulated in the lungs of mice sensitized to that Ag, where it formed large Ab-dependent aggregates in the vasculature. Ag retention in the lungs did not rely on IgG receptors, C1q, neutrophils, or macrophages. IgG2a-mediated, but neither IgG1- nor IgG2b-mediated, passive systemic anaphylaxis led to Ag retention in the lung. Neutrophils and monocytes significantly accumulated in the lungs after challenge and captured high amounts of Ag, which led to downmodulation of surface IgG receptors and triggered their activation. Thus, within minutes of systemic injection in sensitized mice, Ag formed aggregates in the lung and liver vasculature, but accumulated specifically and dose-dependently in the lung. Neutrophils and monocytes recruited to the lung captured Ag and became activated. However, Ag aggregation in the lung vasculature was not necessary for anaphylaxis induction.

Risk factors for severe reactions in food allergy: Rapid evidence review with meta-analysis

This rapid review summarizes the most up to date evidence about the risk factors for severe food-induced allergic reactions. We searched three bibliographic databases for studies published between January 2010 and August 2021. We included 88 studies and synthesized the evidence narratively, undertaking meta-analysis where appropriate. Significant uncertainties remain with respect to the prediction of severe reactions, both anaphylaxis and/or severe anaphylaxis refractory to treatment. Prior anaphylaxis, an asthma diagnosis, IgE sensitization or basophil activation tests are not good predictors. Some molecular allergology markers may be helpful. Hospital presentations for anaphylaxis are highest in young children, yet this age group appears at lower risk of severe outcomes. Risk of severe outcomes is greatest in adolescence and young adulthood, but the contribution of risk taking behaviour in contributing to severe outcomes is unclear. Evidence for an impact of cofactors on severity is lacking, although food-dependent exercise-induced anaphylaxis may be an exception. Some medications such as beta-blockers or ACE inhibitors may increase severity, but appear less important than age as a factor in life-threatening reactions. The relationship between dose of exposure and severity is unclear. Delays in symptom recognition and anaphylaxis treatment have been associated with more severe outcomes. An absence of prior anaphylaxis does not exclude its future risk.

Characterization of hypersensitivity reactions to polysulfone hemodialysis membranes

BACKGROUND

In recent years, cases have been reported in which unexpected systemic hypersensitivity reactions occurred in patients dialyzed with polysulfone- or polyethersulfone-biocompatible membranes in the absence of other risk factors. The pathomechanisms involved in these reactions are largely unknown.

OBJECTIVE

To characterize hypersensitivity reactions to polysulfone hemodialysis using clinical and laboratory data and to identify biomarkers suitable for endotype identification and diagnosis.

METHODS

We prospectively collected data from 29 patients with suspected hypersensitivity reactions to polysulfone hemodialysis membranes. Clinical laboratory parameters such as tryptase, blood cell counts, and complement levels were recorded. Acute samples were obtained from 18 cases for the ex vivo assessment of basophil activation by flow cytometry analysis of CD63, CD203, and FcεRI cell membrane expression. Serum cytokines and anaphylatoxin concentrations were evaluated in 16 cases by Luminex and cytometric bead array analysis.

RESULTS

Tryptase was elevated during the acute reaction in 4 cases. Evidence of basophil activation was obtained in 10 patients. Complement activation was found in only 2 cases. However, C5a serum levels tended to increase during the acute reaction in those patients with hypoxemia. Significantly higher serum levels of interleukin-6 were observed during the acute reactions to polysulfone hemodialysis (P = .0103).

CONCLUSION

Based on biomarker analysis, various endotypes were identified, including type I-like (with the involvement of mast cells or basophils), complement, and cytokine (interleukin-6) release-related reactions, with some patients showing mixed reactions. Further research is needed to unravel the exact mechanisms involved in the activation of these cellular and molecular pathways.

Anaphylaxis knowledge gaps and future research priorities: A consensus report

BACKGROUND

Despite a better understanding of the epidemiology, pathogenesis, and management of patients with anaphylaxis, there remain knowledge gaps. Enumerating and prioritizing these gaps would allow limited scientific resources to be directed more effectively.

OBJECTIVE

We sought to systematically describe and appraise anaphylaxis knowledge gaps and future research priorities based on their potential impact and feasibility.

METHODS

We convened a 25-member multidisciplinary panel of anaphylaxis experts. Panelists formulated knowledge gaps/research priority statements in an anonymous electronic survey. Four anaphylaxis themed writing groups were formed to refine statements: (1) Population Science, (2) Basic and Translational Sciences, (3) Emergency Department Care/Acute Management, and (4) Long-Term Management Strategies and Prevention. Revised statements were incorporated into an anonymous electronic survey, and panelists were asked to rate the impact and feasibility of addressing statements on a continuous 0 to 100 scale.

RESULTS

The panel generated 98 statements across the 4 anaphylaxis themes: Population Science (29), Basic and Translational Sciences (27), Emergency Department Care/Acute Management (24), and Long-Term Management Strategies and Prevention (18). Median scores for impact and feasibility ranged from 50.0 to 95.0 and from 40.0 to 90.0, respectively. Key statements based on median rating for impact/feasibility included the need to refine anaphylaxis diagnostic criteria, identify reliable diagnostic, predictive, and prognostic anaphylaxis bioassays, develop clinical prediction models to standardize postanaphylaxis observation periods and hospitalization criteria, and determine immunotherapy best practices.

CONCLUSIONS

We identified and systematically appraised anaphylaxis knowledge gaps and future research priorities. This study reinforces the need to harmonize scientific pursuits to optimize the outcomes of patients with and at risk of anaphylaxis.

Fatal Food Anaphylaxis: Distinguishing Fact From Fiction

Although there is a general perception that the prevalence of food allergy is increasing, data supporting this are limited. Food is the least common cause of fatal anaphylaxis, and fortunately, it is a very rare event; however, it is also unpredictable. There is widespread consensus that severe reactions cannot be predicted in a clinically meaningful way. Certain food triggers are more frequently associated with fatal anaphylaxis than others. In observational studies, peanut and tree nuts account for at least 30% to 50% of fatalities, with seafood and cow's milk also associated with fatal reactions. Fatal food-induced anaphylaxis is most likely to occur during adolescence and young adulthood, although the reasons for this are unclear. International guidelines agree that intramuscular (IM) epinephrine is the treatment of choice for managing food-triggered anaphylaxis and has a good safety profile when given by the IM route. However, fatalities still occur despite the timely administration of epinephrine. Food-allergic individuals must navigate a world that requires daily vigilance for allergens and preparedness for allergic reactions. Although the actual risk of fatal reactions is minimal, it is not zero, and severe reactions are unpredictable. Clinicians need to help patients better understand the very low but real risk of fatal reaction and enable them to lead as normal a life as possible through appropriate education, safety netting, and risk reduction.

New Biomarkers in Anaphylaxis (Beyond Tryptase)

Purpose of Review

The purpose of this review is to provide a better understanding of anaphylaxis pathophysiology and describe the underlying mechanisms, effector cells, and the potential biomarkers involved depending on the anaphylaxis endotypes.

Recent Findings

New insight into the potential relevance of pathways others than IgE-dependent anaphylaxis has been unraveled, as well as other biomarkers than tryptase, such as the role of platelet activation factor, basogranulin, dipeptidyl peptidase I, CCL-2, and other cytokines.

Summary

Gaining knowledge of all the mediators and cellular activation/communication pathways involved in each endotype of anaphylaxis will allow the application of precision medicine in patients with anaphylactic reactions, providing insights to the most appropriate approach in each case and helping to stratify severity and risk prediction.

Drug-induced anaphylaxis in the emergency department: A prospective observational study

Objective

Anaphylaxis is an acute, life-threatening, systemic hypersensitivity reaction. It is usually triggered by drugs, foods, and insect stings. The primary objective of our study is to determine the factors affecting drug-induced anaphylaxis to contribute to early diagnosis and treatment in these patients.

Methods

Patients over 18 years old who were diagnosed drug-induced anaphylaxis in the Goztepe Hospital within a period of 1 year were evaluated prospectively. Patients demographical data, etiological factors, clinical findings, and treatment information were recorded.

Results

Forty-four patients were enrolled in the study of which 25 (56.8%) were female. The median age of women and men was 54 (min: 22, max 82) and 44 (min 18, max 82), respectively. Twenty-three (52%) of them had a history of anaphylaxis. The most common causes of drug-induced anaphylaxis were antibiotics (36%) and nonsteroidal anti-inflammatory drugs (18%), respectively. Adrenaline was applied to 17 (38%) of the patients in the treatment.

Conclusion

Antibiotics were the most common drugs causing drug-induced anaphylaxis and adrenaline was underused which is the first-line treatment in the anaphylaxis. Some clinicians refrain from administering adrenaline. The reasons underlying this approach should be investigated.

COVID-19 Vaccine Anaphylaxis: Current Evidence and Future Approaches

Vaccine anaphylaxis is rare; however, severe allergic reactions after administration of a coronavirus disease 2019 (COVID-19) vaccines have been reported. Excipients in the vaccine may play a role in severe allergic reactions post-vaccination. Various mechanisms, including IgE-mediated pathways, direct mass cell stimulation via the Mas-related G protein-coupled receptor-X2, and complement pathway activation, have been proposed to cause the anaphylaxis. Skin testing, using the basophil activation test, has been used to clarify the mechanism of the anaphylaxis and provide safety information for the next injection. Here, we review the current evidence and suggested approaches for patients who experienced an immediate severe allergic reaction to the first dose of a COVID-19 vaccine.

Global patterns in anaphylaxis due to specific foods: A systematic review

BACKGROUND

There are increasing global data relating to prevalence of food allergy and food-induced anaphylaxis; however, this is often based on surrogate measures of sensitization rather than objective symptoms at food challenge. In terms of protecting food-allergic consumers from reactions, to our knowledge, there has been no global survey assessing geographic differences in the proportion of anaphylaxis triggered by specific foods.

OBJECTIVE

We sought to identify common triggers for food-induced anaphylaxis and how these vary from country to country.

METHODS

Systematic review of relevant reports published between January 2010 and November 2020. Results were reported following PRISMA guidelines. Publications were screened and data extracted by 2 independent reviewers, and the risk of bias was assessed.

RESULTS

Sixty-five studies (encompassing 41 countries and all 6 regions as defined by the Food and Agriculture Organization of the United Nations) were included. Significant regional variations in the most common triggers of food anaphylaxis were seen; however, in general, there was good agreement between local legislative requirements for allergen disclosure and the most common allergens for each region or nation.

CONCLUSIONS

Local legislation for allergen disclosure generally reflects those allergens commonly responsible for food anaphylaxis. Cow's milk and crustaceans appear to cause a higher proportion of anaphylaxis compared to peanut in some regions.

Pathophysiology of Immunologic and Nonimmunologic Systemic Reactions Including Anaphylaxis

There is a myriad of immunologic and nonimmunologic pathways by which the clinical phenotype of anaphylaxis can be produced. An understanding of these pathways is essential for the prevention as well as the treatment of anaphylactic episodes.

Anaphylaxis: Data Gaps and Research Needs

There are significant anaphylaxis data and knowledge gaps that result in suboptimal patient care and outcomes. To address these gaps there is need for collaborative, multidisciplinary research networks to strategically design practice changing research specific to the following anaphylaxis themes: Population Science, Basic and Translational Sciences, Acute Management, and Long-Term Management. Top priorities are to refine anaphylaxis diagnostic criteria, identify accurate diagnostic and predictive anaphylaxis biomarkers, standardize postanaphylaxis care (observation periods, hospitalization criteria), and determine immunotherapy best practices. Addressing these gaps will result in improved, optimal care and clinical outcomes for patients with or at risk of anaphylaxis.

Overview of Allergy and Anaphylaxis

Allergic reactions and anaphylaxis occur on a severity continuum from mild and self-limited to potentially life-threatening or fatal reactions. Anaphylaxis is typically a multiorgan phenomenon involving a broad range of effector cells and mediators. Emergency department visits for anaphylaxis are increasing, especially among children. There is a broad differential diagnosis for anaphylaxis, and the diagnosis of anaphylaxis can be aided by the use of the National Institutes of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network clinical diagnostic criteria. Risk factors for severe anaphylaxis include older age, delayed epinephrine administration, and cardiopulmonary comorbidities.