Predictors of severe systemic anaphylactic reactions in patients with Hymenoptera venom allergy: importance of baseline serum tryptase-a study of the European Academy of Allergology and Clinical Immunology Interest Group on Insect Venom Hypersensitivity

Evidence-based data support strategies for the prevention of Hymenoptera venom anaphylaxis

PURPOSE OF REVIEW

This review aims to identify phenotypes at-risk of Hymenoptera venom-induced anaphylaxis (HVA), focusing on different perspectives (epidemiological, clinical, and therapeutic) in order to adapt future preventive strategies.

RECENT FINDINGS

HVA remains one of the leading causes of anaphylaxis, with a broad pattern of symptoms. Although most cases occur outside healthcare settings, data indicate a high emergency admission rate due to insect stings. Mortality is often underestimated because of the lack of witnesses and difficulties in recognizing the signs and the culprit. Targeting risk factors could be a clue to improve these statistics and the prognosis of the disease.Potential risk factors for severe HVA in the European population are basal serum tryptase (BST) above 8 μg, mast cell disorders, the absence of skin symptoms, and cardiovascular conditions requiring the use of beta blockers and ACE inhibitors. Identifying these criteria, mainly based on clinical patterns, helps to develop personalized strategies for management and prevention.

SUMMARY

With a personalized medicine approach, phenotypes must be characterized to adapt to the management of patients suffering from Hymenoptera venom anaphylaxis (HVA), including venom immunotherapy (VIT). In this systematic review, all articles mentioned systemic reactions with heterogeneous severity degrees. Half of those reported grade III-IV systemic reactions (Ring and Messmer). HVA clinical patterns could be worsened by one Hymenoptera sting, a patient's history with mast cell disorders, or cardiovascular diseases. VIT failure was attributed to bee venom extract and monotherapy in two-thirds of publications. Findings stress the difficulty of having uniform epidemiological data on HVA and the lack of financial support in some world regions to support appropriate management of these conditions. Although observing a heterogeneity of data, we were able to identify potential risk factors, in particular for the severe cases. We believe our work will support allergists and health professionals to implement improved personalized management of patients suffering from severe HVA.

High burden of clonal mast cell disorders and hereditary α-tryptasemia in patients who need Hymenoptera venom immunotherapy

BACKGROUND

In patients who require venom immunotherapy (VIT), there is a need to identify underlying mast cell (MC) disorders since these may affect the risk and severity of future sting reactions and the long-term effectiveness of VIT.

METHODS

1319 individuals with Hymenoptera venom allergy (HVA) who needed VIT from referral centers in Slovenia, Austria, Croatia, and Poland underwent examination for KIT p.D816V in peripheral blood leukocytes (PBL) using a highly sensitive PCR test and tryptase genotyping by digital droplet PCR. We also included 183 control individuals with large local reactions (LLRs) to Hymenoptera stings and with asymptomatic sensitization to Hymenoptera venoms.

RESULTS

285 of 1319 individuals recommended for VIT (21.6%) were positive for KIT p.D816V in PBL, preferably those who present with severe reaction (33.9% [n = 207 of 610] with Ring-Messmer grade 3-4 vs. 11% [n = 78 of 709] with Grade 1-2; p < .0001), whereas only 1.3% (n = 2 of 152) of controls with LLR and none with asymptomatic sensitization (n = 31) had KIT p.D816V. KIT p.D816V allelic burden was higher in those with severe reaction (median 0.018% [n = 207] in Grade 3-4 vs. 0.001% [n = 78] in Grade 1-2; p < .0001), and the majority had normal baseline serum tryptase levels (69% [n = 196 of 285]). All KIT p.D816V-positive individuals (n = 41) who underwent bone marrow (BM) biopsy were found to have underlying clonal diseases, principally BM mastocytosis. HαT was also associated with severe HVA and symptoms (p < .01), and remarkably, 31.0% (n = 31 of 100) were found to have concomitant KIT p.D816V. Concomitant HαT and KIT p.D816V showed an additive effect, and having both was associated with the highest risk for severe HVA, even higher than having either HαT or KIT p.D816V alone (OR = 3.8; p < .01).

CONCLUSIONS

By employing prospective universal tryptase genotyping and examination for KIT p.D816V in PBL in large HVA populations, we have demonstrated a high burden of clonal MC disorders and HαT in patients who require VIT.

Anaphylaxis in Practice: A Guide to the 2023 Practice Parameter Update

This review summarizes new research developments and clinical practice recommendations for the diagnosis and management of anaphylaxis presented in the Joint Task Force on Practice Parameters 2023 Anaphylaxis practice parameter Update. It is intended to serve as a high-level summary of the 2023 practice parameter, which makes clinically impactful recommendations based on evidence that has emerged since the 2015 practice parameter. We invite clinicians to explore the full 2023 practice parameter to understand the research methods and underlying evidence that have informed the recommendations summarized here. There are new and evolving diagnostic criteria for anaphylaxis, rules for defining elevated tryptase levels, and recognition of signs and symptoms particular to infants and toddlers. The administration of epinephrine should not be used as a surrogate to diagnose anaphylaxis. Risk factors for anaphylaxis should be assessed on a case-by-case basis. Patient counseling and shared decision-making are essential to support patients' treatment decisions and capacity to manage the risk of anaphylaxis at home and in other community settings. Activation of emergency medical services after home epinephrine administration may not be required in all cases, and patients should be engaged in shared decision-making to determine when home management may be appropriate.

Age- and Elicitor-Dependent Characterization of Hymenoptera Venom-Induced Anaphylaxis in Children and Adolescents

BACKGROUND

Hymenoptera venom is one of the most frequent causes of anaphylaxis. Studies from adults indicate the clinical profiles and risk factors of Hymenoptera venom-induced anaphylaxis (VIA). Much less is known about pediatric VIA.

OBJECTIVE

To understand elicitor- and age-related factors determining pediatric VIA by analyzing data from the anaphylaxis registry.

METHODS

We selected pediatric VIA, pediatric food-induced anaphylaxis (FIA), and adult VIA cohorts from the anaphylaxis registry and performed a comparative data analysis regarding elicitors, symptoms, and management.

RESULTS

We identified 725 pediatric patients with VIA, 3,149 with pediatric FIA, and 5,534 with adult VIA. In pediatric VIA, boys were more frequently affected, atopy was not increased, and the onset of the reaction after exposure was fast (≤30 min; 91%) compared with pediatric FIA. Symptoms in pediatric VIA were age dependent, and although respiratory symptoms occurred most frequently besides skin symptoms in both pediatric patients with VIA and FIA, cardiovascular symptoms were more frequently reported in pediatric patients with VIA than pediatric patients with FIA. The analysis of pediatric versus adult VIA revealed clear differences in the frequency of involved organ systems (skin: 93% vs 78%; respiratory: 77% vs 64%; and cardiovascular: 61% vs 85%). For both pediatric and adult VIA, the rates of adrenaline application by a professional were low (29% vs 31%) but hospitalization rates were higher in children than in adults (61% vs 42%). Venom immunotherapy was frequently initiated regardless of age (78% each).

CONCLUSIONS

Pediatric VIA is more frequent in boys, symptoms are age dependent, and hospitalization is often required. Adrenaline should be applied according to current guidelines. Venom immunotherapy is an important treatment option in pediatric VIA and should be considered in severely affected children.

Risk Factors for Severe Sting Reactions and Side Effects During Venom Immunotherapy

Understanding the risk factors leading to severe systemic sting reactions (SSRs) is crucial for initiating venom immunotherapy (VIT) and for educating affected individuals and their families. Some of these risk factors are well established, some are no longer considered risk factors, and some remain controversial. Well-established risk factors for severe SSRs include clonal mast cell disease, high baseline serum tryptase, and advanced age. The absence of skin symptoms and the rapid onset of symptoms are indicators of severe SSRs. Recent publications indicate that antihypertensive treatment and stings in the head and neck area are not risk factors for severe SSRs. VIT is the only available treatment that can potentially prevent further anaphylactic reactions. Although rare and generally manageable, individuals undergoing VIT may experience systemic adverse events (sAEs). More sAEs are expected in patients undergoing bee VIT compared with vespid VIT. The role of elevated baseline serum tryptase as a risk factor for sAEs remains debated, but if it is a factor, the risk is increased by only about 1.5-fold. Rapid updosing protocols, depending on the specific regimen, can also be associated with more sAEs. Severe initial SSRs, antihypertensive medication, high skin test reactivity, and high specific IgE levels are not risk factors for sAEs.

Stinging Ant Anaphylaxis: Advances in Diagnosis and Treatment

Stinging ants represent a wide range of over 200 different species across the world, of which Solenopsis, Myrmecia, Pogonomyrmex, and Brachyponera genera account for a substantial economic and healthcare burden. S. invicta (red imported fire ant [IFA]) and M. pilosula (jack jumper ant [JJA]) are 2 species of high clinical importance, known to cause anaphylaxis in humans, with numerous reported fatalities. Diagnostic testing should be performed in patients with a history of a systemic reaction with skin testing and/or in vitro specific immunoglobulin E (IgE) testing. In vitro testing is commercially available for IFA through whole-body extract specific IgE and JJA venom-specific IgE, but not widely available for other stinging ant species. Commercial venom component testing for IFA and JJA is currently not available. Patients with a clinical history and positive specific IgE testing should undergo treatment with specific immunotherapy, which is currently available for IFA and JJA. Buildup may be performed using conventional, semi-rush, rush, or ultra-rush schedules with similar risk profiles for IFA. Optimal duration for whole=body extract immunotherapy for IFA and specific JJA venom immunotherapy is not well studied, but generally recommended for at least 3 to 5 years. Sting challenges are used in research settings, primarily to assess treatment efficacy of immunotherapy.

Efficacy and safety of hymenoptera venom immunotherapy

Background: Being stung by Hymenoptera species can cause life-threatening anaphylaxis. Although venom immunotherapy (VIT) seems to be the most effective treatment, its long-term efficacy, and risk factors for adverse events remain unclear. Objective: The objective was to investigate the long-term efficacy of VIT and evaluate adverse events and risk factors related to this. Method: Patients who received VIT in a tertiary-care adult allergy clinic between January 2005 and July 2022 were included. Patients' data were compared with those of individuals who had been diagnosed with bee and/or wasp venom allergy during the same period but had not received VIT and experienced field re-stings. Results: The study included 105 patients with venom allergy, of whom 68 received VIT and 37 did not receive VIT. Twenty-three patients (34%) completed 5 years of VIT, and the overall mean ± standard deviation VIT duration was 46.9 ± 20.9 months. Re-stings occurred in 5 of 23 patients who completed 5 years of VIT, and none of them developed a systemic reaction. Eighteen patients (40%) experienced re-stings after prematurely discontinuing VIT, of whom eight (44%) developed a systemic reaction. In the control group of patients who did not receive VIT, 26 patients (70.3%) experienced re-stings, and all had systemic reactions (100%), with no change in their median Mueller scores. There was a significant difference in the median Mueller score change between the patients who received VIT and the controls who did not (p = 0.016). A total of 13 patients (19%) experienced adverse events while receiving VIT, which were systemic reactions in nine honeybee VIT. The use of β-blockers was determined as the most important risk factor (odds ratio 15.9 [95% confidence interval, 1.2-208.8]; p = 0.035). Conclusion: It was confirmed that VIT was effective in both reducing the incidence and the severity of re-sting reactions. These effects were more pronounced in the patients who completed 5 years of VIT.

Basophil Activation Test Predicts Cetuximab Anaphylaxis Severity in Alpha-Gal IgE-Positive Patients

Upon first exposure to cetuximab, hypersensitivity reactions can occur. We aimed to assess the utility of the basophil activation test (BAT) to alpha-gal and cetuximab for predicting severe reactions. We prospectively recruited 38 patients and evaluated sIgE to alpha-gal in all patients before the first application of cetuximab. In all alpha-gal-sensitized patients, we evaluated skin tests to meat extracts, gelatine, and cetuximab and performed BAT with alpha-gal and cetuximab. In 24% (9/38) of patients, sIgE to alpha-gal was >0.10 kUA/L, and 8/9 reacted to the cetuximab. Basophil activation tests with alpha-gal were positive in all sensitized patients and were higher in those with severe reactions (18.3% in grade 4 [n = 4] vs. 1.8% in grade 2 [n = 3] or no reaction [n = 1] at 3.3 ng/mL of alpha-gal; p = 0.03). All patients with severe grade 4 reactions had a positive CD63 BAT response to cetuximab compared to patients with moderate or no reaction, who all had negative BAT (57.7% vs. 0.9% at 500 µg/mL, 63.2% vs. 4.1% at 100 µg/mL, 58.2% vs. 2.7% at 10 µg/mL, and 32.1% vs. 3.3% at 1 µg/mL of cetuximab, respectively; p ≤ 0.001). In summary, before initiating cetuximab treatment, sIgE to alpha-gal should be assessed in all patients. To predict the severity of the reaction and to assess the risk of cetuximab-induced anaphylaxis, we should perform BATs with alpha-gal or more discriminative BATs with cetuximab.

Clinical features, severity, and immunological changes during venom immunotherapy in children and adults

Background: Hymenoptera venom allergy (HVA) is among the most common causes of severe allergic reactions worldwide. Objective: To investigate clinical features and factors that affect the severity of HVA and to determine the alterations in immunologic biomarkers after venom immunotherapy (VIT). Methods: Seventy-six adults and 36 children were prospectively investigated. We analyzed specific immunoglobulin E (sIgE) and sIgG4 levels of venom extracts and components (rApi m1, rApi m10, rVes v1, rVes v5, rPol d5) before and after the first year of VIT. Results: Although cardiovascular symptoms were more common in adults (p < 0.001), the skin was the most affected organ in children (p = 0.009). Serum basal tryptase (sBT) levels were higher in the adults than the children (p < 0.001). The absence of urticaria (odds ratio [OR] 4.208 [95% confidence interval {CI}, 1.395-12.688]; p = 0.011) and sBT ≥ 5.2 ng/mL (OR 11.941 [95% CI, 5.220-39.733]; p < 0.001) were found as the risk factors for grade IV reactions. During VIT, changes in sIgE levels were variable. In the Apis VIT group, we observed remarkable increases in sIgG4 levels in Apis extract and rApi m1 but not in Api m10. Vespula extract, rVes v1, and rVes v5 sIgG4 levels were significantly increased in Vespula VIT group, we also detected significant increases in the Polistes extract and rPol d5 sIgG4 levels, which were not observed in the Apis VIT group. In the patients who received both Apis and Vespula VIT, increases in sIgG4 levels were observed for both venoms. Conclusion: Adults and children can have different clinical patterns. After 1 year, VIT induced a strong IgG4 response. Although Apis immunotherapy (IT) induced Apis sIgG4, excluding Api m10, Vespula IT induced both Vespula and Polistes sIgG4.

Elderly Patients and Insect Venom Allergy: Are the Clinical Pictures and Immunological Parameters of Venom Allergy Age-Dependent?

Insect venom is one of the most common triggers of anaphylaxis in the elderly population. Venom immunotherapy (VIT) remains the only treatment for Hymenoptera venom allergy (HVA). However, little is known about the differences in indication for VIT in the group of patients aged 60 years and older. The objective of this study was to assess the clinical and diagnostic differences of HVA in elderly patients. The study compared data from patients aged ≥ 60 (N = 132) to data from patients aged from 11 to 60 years (N = 750) in terms of HVA severity, comorbidities, and immunological parameters, namely, intradermal testing (IDT), specific IgE (sIgE) levels against extracts and major allergenic molecules, and serum tryptase level (sBT). The severity of systemic HVA (I-IV Müller scale) did not differ between adults and seniors. However, the severity of cardiovascular reactions (IV) increased with age, while the frequency of respiratory reactions (III) decreased. No differences were found in the immunological parameters of sensitization IDT, venom-specific IgE concentrations, or sIgE against Api m 1, 2, 4, 5, and 10 between patients below and above 60 or 65 years of age. Differences were noted for sIgE against Ves v1 and Ves v5; they were higher and lower, respectively, in seniors. In the seniors group, sBT levels were higher. Elevated tryptase levels, along with the aging process, can represent a risk factor within this age category. Nevertheless, advanced age does not influence the immunological parameters of immediate HVA reactions, nor does it impact the diagnosis of HVA.

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.

Clinically accessible amplitude-based multiplex ddPCR assay for tryptase genotyping

Hereditary α tryptasemia (HαT) is an autosomal dominant trait characterized by increased TPSAB1 copy number (CN) encoding α-tryptase. The determination of HαT is being discussed as an important biomarker to be included in risk assessment models and future diagnostic algorithms for patients with mastocytosis and anaphylaxis. Due to the complex genetic structure at the human tryptase locus, genetic testing for tryptase gene composition is presently notably limited and infrequently pursued. This study aimed to develop, optimise and validate a multiplex droplet digital PCR (ddPCR) assay that can reliably quantify α- and β-tryptase encoding sequences in a single reaction. To optimise the ddPCR conditions and establish an amplitude-based multiplex ddPCR assay, additional primers and probes, a thermal gradient with varying annealing temperatures, different primers/probe concentrations, and various initial DNA quantities were tested. Results obtained from all 114 samples analysed using multiplex ddPCR were identical to those obtained through the use of original duplex assays. Utilizing this multiplex ddPCR assay, in contrast to conducting distinct duplex ddPCRs, presents noteworthy benefits for tryptase genotyping. These advantages encompass a substantial threefold decrease in material costs and considerable time savings. Consequently, this approach exhibits high suitability and particularly captures interest for routine clinical implementation.

Case Report: A family history of peanut allergy and hereditary alpha-tryptasemia

Context

Hereditary alpha-tryptasemia (HαT) is associated with elevated basal serum tryptase (bST) and is associated with a higher risk of severe anaphylactic reactions in patients with clonal mast cell disorders or IgE-mediated Hymenoptera venom-induced anaphylaxis. The consequence of this genetic trait remains to be determined in other allergic diseases and food allergy in particular.

Objectives

Here, we describe three cases of peanut allergy among siblings from a single family of four: two of them were associated with HαT, and the third one was associated with the tryptase wild-type genotype.

Methods

TPSAB1/TPSB2 genotypes were determined by digital PCR. After the case description, we provided a review of the literature regarding bST levels and tryptase genotypes in anaphylaxis, with a particular focus on food allergy.

Results

Compared to the sibling with the conventional tryptase genotype, the two siblings with HαT presented a lower peanut threshold at the initial oral food challenge, higher peanut skin prick test reactivity, higher levels of specific IgE to peanut, Ara h 2, and Ara h 6, and a lower IgG4/IgE ratio after 10 years of oral immunotherapy.

Conclusion

The tryptase genotype and HαT status might modify the clinical presentation and biological features of food allergy.

Clinician awareness of the risk of anaphylaxis in patients with cutaneous mastocytosis

The risk of anaphylaxis in maculopapular cutaneous mastocytosis (otherwise known as urticaria pigmentosa) is thought to be approximately 15%. Our survey of British Association of Dermatologists members elicited 40 responses: in patients with normal tryptase levels, adrenaline autoinjectors were prescribed for 10% of adults and 12% of children, increasing to 28% and 30% in those with raised tryptase. Of the 40 respondents, 95% felt a guideline would be beneficial. Thus, we propose a call for a guideline to assist clinicians with management of anaphylaxis risk in such patients, given the rarity of this condition.

Severe food allergy reactions are associated with α-tryptase

BACKGROUND

Increased TPSAB1 copy numbers encoding ⍺-tryptase are associated with severe reactions in adults with Hymenoptera venom allergy, systemic mastocytosis, and idiopathic anaphylaxis.

OBJECTIVE

The primary objective was to assess the association between ⍺-tryptase and severity of food allergy.

METHODS

A total of 119 subjects underwent tryptase genotyping; 82 of them were from an observational food allergy cohort at the National Institute of Allergy and Infectious Disease (NIAID), and 37 were from a cohort of children who reacted to peanut oral food challenge (OFC) at Lurie Children's Hospital of Chicago. The primary predictor was presence or absence of ⍺-tryptase. The primary outcomes for both cohorts were measures of severity of food allergy reaction. Secondary outcomes included OFC symptom scores (Bock/Practical Allergy [PRACTALL] and Severity Grading Score for Acute Reactions [SGSAR]). Correlation between total α-tryptase isoforms and OFC scores was also assessed to account for gene dosage effects.

RESULTS

Among the subjects in the NIAID cohort, the presence of ⍺-tryptase was associated with a higher prevalence of food-triggered anaphylaxis than in those with only β-tryptase (P = .026). Similarly, only 1 of 6 subjects in the OFC cohort with only β-tryptase (17%) had a severe reaction, whereas 20 of 31 of subjects with α-tryptase (65%) had a severe reaction (P = .066). Subjects with ⍺-tryptase also had higher total SGSAR scores than did the subjects with no ⍺-tryptase (P = .003). In addition, there were also significant positive correlations between ⍺-tryptase isoform copy numbers and both higher total SGSAR and Bock/PRACTALL OFC scores (P = .008 and P = .003, respectively).

CONCLUSION

The presence of α-tryptase in subjects is correlated with a higher prevalence of anaphylaxis or severe reaction to food than in subjects without any α-tryptase.

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.

Comparison of recent anaphylaxis diagnostic criteria in real life: Can more patients be diagnosed as having anaphylaxis?

Introduction

In 2020, World Allergy Organization (WAO) updated their diagnostic criteria for anaphylaxis, which differed as a result from the National Institute of Allergy and Infectious Diseases/Food Allergy and Anaphylaxis Network (NIAID/FAAN) criteria which were still used in the 2021 update of the European Academy of Allergy and Clinical Immunology (EAACI) anaphylaxis guideline. Our aim was to evaluate and to compare both diagnostic criteria and attempt to identify factors affecting severity of anaphylaxis.

Methods

The medical records of the patients who were evaluated with suspected anaphylaxis at 3 medical centers in Türkiye between 2014 and 2021, and underwent a detailed diagnostic work-up, were analyzed retrospectively. Diagnosis of anaphylaxis was evaluated based on the WAO 2020 and EAACI 2021 and NIAID/FAAN diagnostic criteria. The severity of anaphylaxis was determined according to the WAO systemic allergic reaction grading system. Grade 5 anaphylaxis was defined as having respiratory failure, collapse/hypotension, loss of consciousness. Patients' demographic and clinical characteristics were further analyzed depending on the severity of the reaction.

Results

One thousand and six patients were evaluated and 232 patients without a convincing diagnosis of anaphylaxis were excluded from the study. The remaining 774 patients (70.6% female, median [Inter quartile range (IQR) 25-75] age: 42 [33-52]) were included for further examination. Anaphylaxis was diagnosed in 729 (94.2%) patients meeting both criteria whereas 35 patients (4.5%) with isolated laryngeal involvement and 10 (1.3%) patients with isolated respiratory involvement were only diagnosed according to the WAO 2020 criteria. Twenty-three patients (3.0%) had a diagnosis of indolent systemic mastocytosis. Mastocytosis was related to grade 5 anaphylaxis [p = 0.022, OR (CI) = 2.9 (1.1-7.6)]. Venom allergy was a risk factor for grade 5 anaphylaxis among those for whom an eliciting allergen could be determined [p = 0.03, OR (CI) = 2.7 (1.1-6.8)]. For drug induced anaphylaxis, parenteral route of drug administration and proton pump inhibitor (PPI) allergy were considered as risk factors for grade 5 anaphylaxis [p < 0.001, OR (CI) = 6.5 (2.5-17.0); p = 0.011, OR (CI) = 10.3 (1.6-63.3)].

Conclusion

This multicenter study demonstrated that both criteria identified the majority of patients with anaphylaxis, but the WAO 2020 diagnostic criteria identified an additional 6%. Hymenoptera stings, PPI allergy, parenteral drug administration, and underlying mastocytosis were associated with more severe episodes.

Disease Spectrum of Anaphylaxis Disorders

Anaphylaxis results from massive mast cell activation. Mechanisms of mast cell activation may involve IgE- and non-IgE-mediated triggers, clonal mast cell disease, or be idiopathic and may be modified by several factors including but not restricted to hormonal status, stress, heritable factors, mast cell burden, and simultaneous exposure to more than 1 factor. Patients with recurrent anaphylaxis with a nonidentifiable trigger present a particular challenge in diagnosis and management. Presence of clonal disease may be suggested by hypotensive episodes with urticaria and angioedema, and high baseline tryptase levels. A number of scoring systems have been developed to identify patients who are at high risk to have underlying mastocytosis. This review provides an overview of anaphylaxis disorders and our current understanding of their mechanisms of action, evaluation, and management.

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.

Cofactors in food anaphylaxis in adults

Around 25% to 50% of food-induced allergic reactions in adults cause anaphylaxis, and epidemiologic evidence suggests that food is the most common cause of anaphylaxis. Reaction severity is unpredictable, and patients will often experience reactions of variable severity, even to an identical exposure (both dose and allergen). A common explanation for this phenomenon has been the impact of "cofactors"-factors that might contribute to reaction severity independent of the allergen exposure. Cofactors can influence reaction severity in 2 ways: either by reducing the reaction threshold (ie, the dose needed to trigger any symptoms) so that patients have no symptoms in the absence of the cofactor and only react with the cofactor present, or by increasing reaction severity such that individuals have only mild symptoms in the absence of the cofactor, but a more severe reaction when the cofactor is present. Indeed, the same patient may have reactions with different cofactors or even need more than one cofactor to develop a severe reaction. Cofactors reportedly play a role in approximately 30% of anaphylaxis reactions in adults. Exercise, nonsteroidal, anti-inflammatory drugs, alcohol, and sleep deprivation are the most frequent cofactors reported. Routine evaluation of the possible involvement of cofactors is essential in managing patients with food anaphylaxis: in patients with a suggestive history but a negative oral food challenge, cofactors should be taken into account to provide appropriate advice to reduce the risk of future anaphylaxis.

Tryptase in type I hypersensitivity

Tryptase is currently the main mast cell biomarker available in medical practice. Tryptase determination is a quantitative test performed in serum or plasma for the diagnosis, stratification, and follow-up of mast cell-related conditions. The continuous secretion of monomeric α and β protryptases forms the baseline tryptase level. Transient, activation-induced release of tryptase is known as acute tryptase. Because mast cells are tissue-resident cells, the detection of an acute tryptase release in the bloodstream is protracted, with a delay of 15 to 20 minutes after the onset of symptoms and a peak at approximately 1 hour. Constitutive release of tryptase is a marker of mast cell number and activity status, whereas transient release of mature tryptase is a marker of mast cell degranulation. Although consensual as a concept, the application of this statement in clinical practice has only been clarified since 2020. For baseline tryptase to be used as a biomarker, reference values need to be established. In contrast, defining a transient increase using acute tryptase can only be achieved as a function of the baseline status.

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.

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.

Systemic Mastocytosis in a Patient with BCR-ABL1-Positive Chronic Myeloid Leukemia in the Remission Phase

Systemic mastocytosis (SM) comprises a group of rare disorders resulting from tissue infiltration by pathological mast cells. In a percentage ranging from 5 to 40% in various patient series, SM appears to be associated with an accompanying hematologic neoplasm (SM-AHN). The coexistence of SM with chronic myelogenous leukemia (CML) is extremely rare with only 3 cases in the literature. The natural course of CML has changed dramatically over the past 2 decades with the use of tyrosine kinase inhibitors (TKIs). We report a case of diagnosing SM in a patient in complete molecular remission of CML after stopping TKI treatment.

Overexpression of FcεRI on Bone Marrow Mast Cells, but Not MRGPRX2, in Clonal Mast Cell Disorders With Wasp Venom Anaphylaxis

Background

Uncertainties remain about the molecular mechanisms governing clonal mast cell disorders (CMCD) and anaphylaxis.

Objective

This study aims at comparing the burden, phenotype and behavior of mast cells (MCs) and basophils in patients with CMCD with wasp venom anaphylaxis (CMCD/WVA⁺), CMCD patients without anaphylaxis (CMCD/ANA^-), patients with an elevated baseline serum tryptase (EBST), patients with wasp venom anaphylaxis without CMCD (WVA⁺) and patients with a non-mast cell haematological pathology (NMHP).

Methods

This study included 20 patients with CMCD/WVA⁺, 24 with CMCD/ANA^-, 19 with WVA⁺, 6 with EBST and 5 with NMHP. We immunophenotyped MCs and basophils and compared baseline serum tryptase (bST) and both total and venom specific IgE in the different groups. For basophil studies, 13 healthy controls were also included.

Results

Higher levels of bST were found in CMCD patients with wasp venom anaphylaxis, CMCD patients without anaphylaxis and EBST patients. Total IgE levels were highest in patients with wasp venom anaphylaxis with and without CMCD. Bone marrow MCs of patients with CMCD showed lower CD117 expression and higher expression of CD45, CD203c, CD63, CD300a and FcεRI. Within the CMCD population, patients with wasp venom anaphylaxis showed a higher expression of FcεRI as compared to patients without anaphylaxis. Expression of MRGPRX2 on MCs did not differ between the study populations. Basophils are phenotypically and functionally comparable between the different patient populations.

Conclusion

Patients with CMCD show an elevated burden of aberrant activated MCs with a significant overexpression of FcεRI in patients with a wasp venom anaphylaxis.

Workup and Clinical Assessment for Allergen Immunotherapy Candidates

Allergen Immunotherapy (AIT) is a well-established, efficient, and safe way to treat respiratory and insect-venom allergies. After determining the diagnosis of the clinically relevant culprit allergen, AIT can be prescribed. However, not all patients are eligible for AIT, since some diseases/conditions represent contraindications to AIT use, as described in several guidelines. Allergists are often preoccupied on whether an extensive workup should be ordered in apparently healthy AIT candidates in order to detect contra-indicated diseases and conditions. These preoccupations often arise from clinical, ethical and legal issues. The aim of this article is to suggest an approach to the workup and assessment of the presence of any underlying diseases/conditions in patients with no case history before the start of AIT. Notably, there is a lack of published studies on the appropriate evaluation of AIT candidates, with no globally accepted guidelines. It appears that Allergists are mostly deciding based on their AIT training, as well as their clinical experience. Guidance is based mainly on experts’ opinions; the suggested preliminary workup can be divided into mandatory and optional testing. The evaluation for possible underlying neoplastic, autoimmune, and cardiovascular diseases, primary and acquired immunodeficiencies and pregnancy, might be helpful but only in subjects for whom the history and clinical examination raise suspicion of these conditions. A workup without any reasonable correlation with potential contraindications is useless. In conclusion, the evaluation of each individual candidate for possible medical conditions should be determined on a case-by-case basis.

Mucosal Mast Cells as Key Effector Cells in Food Allergies

Mucosal mast cells (MMCs) localized in the intestinal mucosa play a key role in the development of IgE-mediated food allergies. Recent advances have revealed that MMCs are a distinctly different population from connective tissue mast cells localized in skin and other connective tissues. MMCs are inducible and transient cells that arise from bone marrow-derived mast cell progenitors, and their numbers increase rapidly during mucosal allergic inflammation. However, the mechanism of the dramatic expansion of MMCs and their cell functions are not well understood. Here, we review recent findings on the mechanisms of MMC differentiation and expansion, and we discuss the potential for the inducers of differentiation and expansion to serve as targets for food allergy therapy. In addition, we also discuss the mechanism by which oral immunotherapy, a promising treatment for food allergy patients, induces unresponsiveness to food allergens and the roles of MMCs in this process. Research focusing on MMCs should provide useful information for understanding the underlying mechanisms of food allergies in order to further advance the treatment of food allergies.

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.

Repeated adrenaline requirements for anaphylaxis

We examined the pattern of adrenaline administration in patients presenting with anaphylaxis. Forty-four percent required repeated adrenaline administration, among whom there had been greater cardiorespiratory compromise. Repeated administration was more frequent in males and older patients, and those triggered by insect sting or unknown cause; no other patient factors were identified. This study supports the provision of two adrenaline auto-injectors to all anaphylaxis patients.

Anaphylaxis and Mast Cell Disorders

There is strong evidence of an association between severe anaphylaxis, especially hymenoptera venom induced, and mast cell (MC) disorders. It has been thought that intrinsic abnormalities in MCs, including the presence of the activating KIT D816V mutation in mastocytosis or of genetic trait, hereditary alpha-tryptasemia, may influence susceptibility to severe anaphylaxis. This article evaluates the potential mechanisms leading to severe MC activation, as well as the differential diagnosis of and range of symptoms attributable to MC mediator release. Also, we offer a global classification for disorders related to MC activation.

Anaphylaxis to Stinging Insect Venom

Hymenoptera stinging insects are common culprits for allergic reactions. Anaphylaxis to insect stings can be life threatening and is associated with a significant risk of recurrence. Insect allergy requires referral to an allergist/immunologist for education and for diagnostic evaluation that will direct further management and treatment. Venom immunotherapy is safe and effective; it prevents sting anaphylaxis in up to 98% of patients. Potential risk factors for side effects during testing and treatment should be assessed for every patient to mitigate risk and to guide treatment recommendations and the duration of immunotherapy.

Allergic reactions due to concomitant administration of multiple drugs in intravenous fluid in emergency departments in Turkey

The present study aimed to evaluate patients who were referred to adult allergy clinic due to allergic reactions after concomitant multiple intravenous-drug administrations in Emergency Department (ED). Between January 2017 and January 2019, patients admitted to our allergy clinic with hypersensitivity reactions to intravenous drugs administered in ED were included retrospectively. Fifty-seven patients who developed allergic reactions after intravenous drug administration in EDs were evaluated. Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) were the most common cause of allergic reactions (n = 40, 70.2%). Skin Prick Tests (SPT) were positive in 6 (10.5%) patients. Drug Provocation Tests (DPT) were positive in 10 (17.5%) patients. No significant correlation was found between the total number of drugs in the intravenous fluid and the degree of allergic reaction (r = -0.145, p = 0.282). There was no statistically significant difference between the degree of allergic reaction and history of atopic disease (p = 0.579). In conclusion, concomitant administration of multiple drugs in intravenous fluids may increase the risk of allergic reactions.

[Allergen immunotherapy: FAQs and facts]

Die Allergenimmuntherapie (AIT) ist – neben der oft nicht suffizient durchzuführenden Allergenmeidung – die einzige kausale Therapie Ig(Immunglobulin)E-vermittelter Allergien gegen Aeroallergene und Hymenopterengifte. Sie kann je nach Allergen als subkutane Injektion (subkutane Immuntherapie [SCIT]) oder über eine sublinguale Applikation (sublinguale Immuntherapie [SLIT]) erfolgen, kürzlich wurde zudem auch ein Verfahren zur oralen Immuntherapie zur Behandlung der Nahrungsmittelallergie zugelassen. Neben der korrekten Indikationsstellung (positive Anamnese und Diagnostik einer IgE-vermittelten Allergie, Allergenkarenz nicht ausreichend möglich) sind mögliche Kontraindikationen und Risikofaktoren zu beachten. Zudem kann es unter einer AIT zu – potenziell auch lebensgefährlichen – Nebenwirkungen kommen. Im Folgenden sollen häufig gestellte Fragen und Fakten zur Entscheidungsfindung für die Durchführung und zum Risikomanagement der AIT beleuchtet und unter Berücksichtigung der aktuellen Datenlage diskutiert werden.

Hymenoptera venom-induced anaphylaxis and hereditary alpha-tryptasemia

PURPOSE OF REVIEW

To discuss the association between the common dominantly inherited genetic trait hereditary alpha-tryptasemia (HαT) and hymenoptera venom-induced anaphylaxis (HVA).

RECENT FINDINGS

Elevated BST has been correlated with more severe systemic anaphylaxis in humans in a number of settings - most notably in HVA. Clonal mast cell disease, in particular, systemic mastocytosis, is frequently associated with elevated BST, and is a major risk factor for severe HVA. However, clonal mast cell diseases are believed to be rare, whereas HVA is relatively more common. HαT affects an estimated 3-5% of Western populations and is the common cause for elevated BST in these individuals. An association between HαT and severe HVA, as well as clonal mast cell disease has recently been demonstrated wherein this trait modifies reaction severity in venom allergic individuals. A mechanism underlying this association has been proposed through the identification of naturally occurring heterotetrameric tryptases and characterization of their unique physical attributes.

SUMMARY

Here we discuss the long-standing association between elevated BST and HVA severity, how HαT fits into this landscape, and review the clinical and mechanistic evidence that supports HαT as a modifier of HVA.

Routine KIT p.D816V screening identifies clonal mast cell disease in patients with Hymenoptera allergy regularly missed using baseline tryptase levels alone

BACKGROUND

Clonal mast cell disorders and elevated basal serum tryptase (BST) levels with unknown cause(s) are associated with severe Hymenoptera venom-triggered anaphylaxis (HVA). However, some individuals with clonal disease have a normal BST level (<11.4 ng/mL).

OBJECTIVE

Our aim was to evaluate whether screening for KIT p.D816V in the blood is a useful clinical tool to risk-stratify patients with venom allergy.

METHODS

We prospectively recruited 374 patients with Hymenoptera allergy and no overt signs of mastocytosis who were referred to our center during the years 2018 and 2019. KIT p.D816V was determined in their peripheral blood by quantitative PCR, and tryptase genotyping was performed by droplet digital PCR.

RESULTS

In all, 351 patients (93.9%) had normal levels of BST, and KIT p.D816V was detected in 8% of patients (28 of 351), predominantly in patients with the most severe Mueller grade IV anaphylaxis (18.2% [24 of 132] vs 1.8% in patients with lower grades [4 of 88 with grade III and 0 of 131 with other grades]; P < .001). In grade IV patients with a normal BST level, KIT p.D816V was associated with more severe symptoms, including a significantly higher frequency of loss of consciousness (58.3% [14 of 24] vs 34.3% [37 of 108]; P = .03) and absence of skin symptoms (41.7% [10 of 24] vs 15.7% [17 of 108]; P = .004). Among patients with a normal BST level, KIT p.D816V (OR = 10.25 [95% CI = 3.75-36.14]; P < .0001) was the major risk factor associated with severe HVA. Hereditary α-tryptasemia (HαT) due to increased germline copies of TPSAB1 encoding α-tryptase was the most common cause (65.2% [15 of 23]) of elevated BST level in patients with HVA, and together with KIT p.D816V, it accounted for 90% of BST level elevations (20 of 23) in patients with HVA.

CONCLUSION

These results indicate that routine KIT p.D816V screening identifies clonal disease in high-risk patients with HVA who are regularly missed when BST level is used alone.

β-blockers and ACE inhibitors are not a risk factor for severe systemic sting reactions and adverse events during venom immunotherapy

Background

There is controversy whether taking β‐blockers or ACE inhibitors (ACEI) is a risk factor for more severe systemic insect sting reactions (SSR) and whether it increases the number or severity of adverse events (AE) during venom immunotherapy (VIT).

Methods

In this open, prospective, observational, multicenter trial, we recruited patients with a history of a SSR and indication for VIT. The primary objective of this study was to evaluate whether patients taking β‐blockers or ACEI show more systemic AE during VIT compared to patients without such treatment.

Results

In total, 1,425 patients were enrolled and VIT was performed in 1,342 patients. Of all patients included, 388 (27.2%) took antihypertensive (AHT) drugs (10.4% took β‐blockers, 11.9% ACEI, 5.0% β‐blockers and ACEI). Only 5.6% of patients under AHT treatment experienced systemic AE during VIT as compared with 7.4% of patients without these drugs (OR: 0.74, 95% CI: 0.43–1.22, p = 0.25). The severity of the initial sting reaction was not affected by the intake of β‐blockers or ACEI (OR: 1.14, 95% CI: 0.89–1.46, p = 0.29). In total, 210 (17.7%) patients were re‐stung during VIT and 191 (91.0%) tolerated the sting without systemic symptoms. Of the 19 patients with VIT treatment failure, 4 took β‐blockers, none an ACEI.

Conclusions

This trial provides robust evidence that taking β‐blockers or ACEI does neither increase the frequency of systemic AE during VIT nor aggravate SSR. Moreover, results suggest that these drugs do not impair effectiveness of VIT. (Funded by Medical University of Graz, Austria; Clinicaltrials.gov number, NCT04269629).

Conducting an Oral Food Challenge: An Update to the 2009 Adverse Reactions to Foods Committee Work Group Report

Oral food challenges are an integral part of an allergist's practice and are used to evaluate the presence or absence of allergic reactivity to foods. A work group within the Adverse Reactions to Foods Committee of the American Academy of Allergy, Asthma & Immunology was formed to update a previously published oral food challenge report. The intention of this document was to supplement the previous publication with additional focus on safety, treatment of IgE-mediated allergic reactions, guidance for challenges in infants and adults, psychosocial considerations for children and families participating in an oral food challenge, specific guidance for baked milk or baked egg challenges, masking agents and validated blinding recipes for common food allergens, and recommendations for conducting and interpreting challenges in patients with suspected food protein-induced enterocolitis syndrome. Tables and figures within the report and an extensive online appendix detail age-specific portion sizes, appropriate timing for antihistamine discontinuation, serum and skin test result interpretation, written consents, and instructional handouts that may be used in clinical practice.

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.

Biomarkers of the Severity of Honeybee Sting Reactions and the Severity and Threshold of Systemic Adverse Events During Immunotherapy

BACKGROUND

A biomarker that could identify individuals at high risk for severe honeybee sting allergic reaction and/or systemic adverse events (SAEs) during venom immunotherapy (VIT) would improve the management of patients with honeybee (HB) venom allergy.

OBJECTIVE

To identify biomarkers for risk of severe sting reactions or SAEs during VIT.

METHODS

We recruited 332 patients undergoing HB VIT. We ascertained predictors of the severity of the field-sting reaction and the severity and threshold of SAEs during VIT. We assessed the use of cardiovascular medications; baseline serum tryptase (BST) levels; specific IgEs to HB venom, rApi m 1, and rApi m 10; and basophil activation test (BAT) response.

RESULTS

Significant and independent predictors of a severe HB field-sting reaction were age (P = .008), an absence of skin symptoms (P = .001), BST (P = .014), and BAT response at an HB venom concentration of 0.1 μg/mL (P = .001). Predictors of severe SAEs during HB VIT were age (P = .025), BST (P = .006), and BAT response (P = .001). BAT response was also an individual and significant predictor of any SAEs and SAEs at a low cumulative allergen dose (median, 55 μg) during VIT build-up (P < .001). The use of β-blockers and angiotensin-converting-enzyme inhibitors and specific IgE levels were not associated with the severity of HB field-sting reactions or VIT SAEs.

CONCLUSIONS

BST and basophil activation are independent risk factors for severe HB sting anaphylaxis and SAEs during HB VIT. BAT response was the best biomarker for any SAEs and a lower threshold of SAEs during HB VIT. These risk factors can help guide recommendations for VIT and overcome systemic reactions to HB VIT.

Clinical effects and factors associated with adverse clinical outcomes of hymenopteran stings treated in a Thai Poison Centre: a retrospective cross-sectional study

OBJECTIVE

To describe clinical effects and outcomes of hymenopteran stings and to explore the non-laboratory factors associated with adverse clinical outcomes, a composite outcome including death, respiratory failure requiring intubation, acute kidney injury (AKI) requiring dialysis and hypotension requiring vasopressor use.

METHODS

A retrospective cross-sectional study was performed at the Ramathibodi Poison Center, a poison centre of a tertiary care hospital in Thailand. All cases of hymenopteran sting consultations from January 2015 to June 2019 were consecutively enrolled, and charts were reviewed. Demographics, initial clinical characteristics and outcomes were collected. Factors associated with adverse clinical outcome were explored.

RESULTS

One hundred and fourteen hymenopteran stings cases (wasp 48%, bee 33%, hornet 14% and carpenter bee 8.8%) were included (median age, 36.5 years (interquartile range 9-55); male 63%). The prevalence of adverse clinical outcomes was 12.3% (95%CI 6.88-12.8). At initial presentation, 100% of cases had local skin reactions, 11.4% were clinical anaphylaxis, and 8% had red urine. Adverse clinical outcomes included death (n = 10), respiratory failure requiring intubation (n = 9), AKI requiring dialysis (n = 6) and hypotension requiring vasopressor use (n = 2). None of the patients with carpenter bee or hornet stings developed adverse clinical outcomes. In univariable analysis, urticaria, wheezing, red urine, wasp sting and sting number > 10 were significantly associated with adverse clinical outcomes. In multivariable analysis, red urine (adjusted OR 11.1 (95% CI 1.57-216)), wheezing (adjusted OR 16.7 (95% CI 1.43-402)) and a number of stings > 10 (adjusted OR 21.5 (95% CI2.13-2557)) were significant.

CONCLUSIONS

Adverse clinical outcomes in hymenopteran stings were not uncommon among cases inquiring to a national Thai poison centre. At initial presentation, red urine, wheezing and a number stings >10 were significantly associated with adverse clinical outcomes. Larger epidemiologic studies are required to confirm these associations.

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.

Prevalence of mastocytosis and hymenoptera venom allergy in the United States

BACKGROUND

Mastocytosis is a risk factor for hymenoptera venom anaphylaxis (HVA). Current guidelines recommend measuring tryptase in patients with HVA and that those with mastocytosis pursue lifelong venom immunotherapy (VIT). Available data on HVA and mastocytosis largely derive from European single-center studies, and the prevalence of HVA with and without mastocytosis in the United States is unknown.

OBJECTIVE

We sought to determine the prevalence of HVA and mastocytosis in the United States using an insurance claims database and evaluate the impact of mastocytosis on VIT in patients with HVA in a US cohort.

METHODS

The IBM Watson Database, consisting of insurance claims from approximately 27 million US patients in 2018, was queried to identify patients with HVA and/or mastocytosis. Furthermore, a retrospective study of 161 patients undergoing VIT between 2015 and 2018 at the University of Michigan was conducted.

RESULTS

In the IBM Watson Database, the prevalence of HVA was 167 per 100,000 (0.167%) and the prevalence of mastocytosis 10 per 100,000 (0.010%) overall and 97 per 100,000 (0.097%) among those with HVA. Mastocytosis showed a 9.7-fold increase among patients with HVA versus the general population. In the U-M cohort, 2.6% of patients with VIT had mastocytosis. Tryptase level did not correlate with venom reaction severity but was higher in patients with systemic VIT reactions.

CONCLUSIONS

We observed a lower US HVA prevalence than previously reported. Mastocytosis was more common in US patients with HVA, though at lower rates than previously reported. In patients with VIT there was no correlation between tryptase level and reaction severity.

Hereditary α tryptasemia is a valid genetic biomarker for severe mediator-related symptoms in mastocytosis

Mastocytosis is a hematopoietic neoplasm characterized by expansion of KIT D816V-mutated clonal mast cells in various organs and severe or even life-threatening anaphylactic reactions. Recently, hereditary α-tryptasemia (HαT) has been described as a common genetic trait with increased copy numbers of the α-tryptase encoding gene, TPSAB1, and associated with an increased basal serum tryptase level and a risk of mast cell activation. The purpose of our study was to elucidate the clinical relevance of HαT in patients with mastocytosis. TPSAB1 germline copy number variants were assessed by digital polymerase chain reaction in 180 mastocytosis patients, 180 sex-matched control subjects, 720 patients with other myeloid neoplasms, and 61 additional mastocytosis patients of an independent validation cohort. α-Tryptase encoding TPSAB1 copy number gains, compatible with HαT, were identified in 17.2% of mastocytosis patients and 4.4% of the control population (P < .001). Patients with HαT exhibited higher tryptase levels than patients without HαT (median tryptase in HαT+ cases: 49.6 ng/mL vs HαT- cases: 34.5 ng/mL, P = .004) independent of the mast cell burden. Hymenoptera venom hypersensitivity reactions and severe cardiovascular mediator-related symptoms/anaphylaxis were by far more frequently observed in mastocytosis patients with HαT than in those without HαT. Results were confirmed in an independent validation cohort. The high prevalence of HαT in mastocytosis hints at a potential pathogenic role of germline α-tryptase encoding TPSAB1 copy number gains in disease evolution. Together, our data suggest that HαT is a novel emerging robust biomarker in mastocytosis that is useful for determining the individual patient´s risk of developing severe anaphylaxis.

Fatal Anaphylaxis: Epidemiology and Risk Factors

PURPOSE OF REVIEW

To provide clinicians with an understanding of risk factors associated with fatal anaphylaxis, and to promote individualized management plans with patients based upon key aspects of their clinical history.

RECENT FINDINGS

While anaphylaxis can affect a significant percentage of the general population, death from anaphylaxis remains a rare outcome. The presence of asthma and peanut or tree nut allergy is associated with higher risk for severe or fatal anaphylaxis from foods. Specific triggers (medications, venom), underlying comorbid conditions, age, and use of some medications can also impact risk and warrant different counseling and management strategies. Anaphylaxis is a rapidly progressive systemic reaction with multiple different causes and encompasses a wide degree of severity in clinical presentation and risk for future episodes. Individualized management, discussion of risk, and shared decision making should occur with each patient and in consideration of their personal risk factors.

Use and Interpretation of Acute and Baseline Tryptase in Perioperative Hypersensitivity and Anaphylaxis

Paired acute and baseline serum or plasma tryptase sampling and determination have recently been included as a mechanistic approach in the diagnostic and management guidelines of perioperative immediate hypersensitivity and anaphylaxis. The timing of this paired sampling is clearly defined in international consensus statements, with the optimal window for acute tryptase sampling between 30 minutes and 2 hours after the initiation of symptoms, whereas baseline tryptase should be measured in a sample collected before the event (preop) or at least 24 hours after all signs and symptoms have resolved. A transient elevation of the acute tryptase level greater than [2 + (1.2 × baseline tryptase level)] supports the involvement and activation of mast cells. Here, we provide the clinical, pathophysiological, and technical rationale for the procedure and interpretation of paired acute and baseline tryptase. Clinical examples, up-to-date knowledge of hereditary α-tryptasemia as a frequent cause of baseline tryptase of 7 μg/L and higher, mastocytosis, other clonal myeloid disorders, cardiovascular or renal failure, and technical improvements resulting in continued lowering of the 95th percentile value are discussed. Clues for improved management of perioperative immediate hypersensitivity and anaphylaxis include (1) sustained dissemination and implementation of updated guidelines; (2) preoperative sample storage for deferred analysis; (3) referral for thorough allergy investigation, screening for mast cell-related disorders, and recommendations for future anesthetic procedures; and (4) sustained collaboration between anesthesiologists, immunologists, and allergists.