Mast Cell Activation Syndrome and Mastocytosis: Initial Treatment Options and Long-Term Management

Topical corticosteroids for hives and itch (urticaria): Systematic review and Bayesian meta-analysis of randomized trials

BACKGROUND

Topical corticosteroids are widely used as a treatment for itch and wheals (urticaria), but their benefits and harms are unclear.

OBJECTIVE

To systematically synthesize the benefits and harms of topical corticosteroids for the treatment of urticaria.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL from database inception to March 23, 2024, for randomized trials comparing topical corticosteroids with placebo for patients with urticaria (either chronic spontaneous or inducible urticaria or acute urticaria elicited from skin/intradermal allergy testing). Paired reviewers independently screened records, extracted data, and assessed risk of bias. Random-effects meta-analyses addressed urticaria severity, itch severity (numeric rating scale; range 0-10; higher is worse), and adverse events. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach informed certainty of evidence ratings. PROSPERO registration: CRD42023455182.

RESULTS

A total of 19 randomized controlled trials enrolled 379 participants with a median of mean age of 30.1 (range 21.1-44.0) years. Compared with placebo, topical corticosteroids may reduce wheal size (ratio of means 0.47, 95% CI 0.38-0.59; low certainty) and itch severity (mean difference -1.30, 95% CI -5.07 to 2.46; very low certainty). Topical corticosteroids result in little to no difference in overall adverse events (94 fewer patients per 1000, 95% credible intervals 172 fewer to 12 more; high certainty).

CONCLUSION

Compared with placebo, topical corticosteroids may result in a reduction of wheal size and little to no difference in overall adverse events. Topical corticosteroids may reduce itch severity, but the evidence is very uncertain. Future large, randomized trials addressing the use of topical corticosteroids would further support optimal urticaria management.

Inflammatory pathways in patients with post-acute sequelae of COVID-19: The role of the clinical immunologist

As the SARS-CoV-2 pandemic progressed, some survivors noted prolonged symptoms after acute infection, termed post-acute sequelae of COVID-19 (PASC) or "long COVID." PASC is a significant clinical and public health concern that adversely affects patients' quality of life, income, and health care expenses. Moreover, PASC symptoms are highly heterogeneous, the most common being fatigue and cognitive impairment, and they likely reflect a spectrum of clinical phenotypes. The proposed role of persistent inflammation is one of leading pathophysiological theories. This review article addresses these proposed mechanisms of persistent and aberrant inflammation, their clinical evaluation, and theoretical approaches to management. A review of public databases was used to collect literature for the review. The literature supports a prominent role of persistent and aberrant inflammation as a major contributor to the symptoms of PASC. Proposed mechanisms for persistent inflammation include reactivation of latent viruses, viral persistence, loss of immunoregulatory pathways, autoimmune mechanisms, and/or mast cell dysregulation. Persistent inflammation may result in constitutional symptoms such as fatigue, brain fog, body aches, and/or organ-specific dysfunction, such as gastrointestinal dysregulation and myocardial inflammation. There are no approved or even proven therapies for PASC at this time, but some studies have identified therapeutic options that may either reduce the risk for progression to PASC or decrease symptom burden. Laboratory evaluation and therapeutic options are limited and require further investigation to establish their clinical value. A more refined definition of PASC is needed to address the wide variety of clinical presentations, pathophysiology, and therapeutic options.

Mast cell activation syndrome: Current understanding and research needs

Mast cell activation syndrome (MCAS) is a term applied to several clinical entities that have gained increased attention from patients and medical providers. Although several descriptive publications about MCAS exist, there are many gaps in knowledge, resulting in confusion about this clinical syndrome. Whether MCAS is a primary syndrome or exists as a constellation of symptoms in the context of known inflammatory, allergic, or clonal disorders associated with systemic mast cell activation is not well understood. More importantly, the underlying mechanisms and pathways that lead to mast cell activation in MCAS patients remain to be elucidated. Here we summarize the known literature, identify gaps in knowledge, and highlight research needs. Covered topics include contextualization of MCAS and MCAS-like endotypes and related diagnostic evaluations; mechanistic research; management of typical and refractory symptoms; and MCAS-specific education for patients and health care providers.

Functions of methyltransferase-like 3 in breast cancer: pathogenesis, drug resistance, and therapeutic target

Breast cancer (BC) is a highly prevalent malignancy worldwide, with complex pathogenesis and treatment challenges. Research reveals that methyltransferase-like 3 (METTL3) is widely involved in the pathogenesis of several tumors through methylation of its target RNAs, and its role and mechanisms in BC are also extensively studied. In this review, we aim to provide a comprehensive interpretation of available studies and elucidate the relationship between METTL3 and BC. This review suggests that high levels of METTL3 are associated with the pathogenesis, poor prognosis, and drug resistance of BC, suggesting METTL3 as a potential diagnostic or prognostic biomarker and therapeutic target. Collectively, this review provides a comprehensive understanding of how METTL3 functions through RNA methylation, which provides a valuable reference for future fundamental studies and clinical applications.

SOHO State of the Art Update and Next Questions: Current and Emerging Therapies for Systemic Mastocytosis

Systemic mastocytosis (SM) is a heterogeneous myeloid neoplasm, characterized by clonal proliferation of mast cells (MCs) in ≥ 1 extracutaneous organs, including the bone marrow (BM) and gastrointestinal tract. Aberrant MC proliferation is driven by mutation KIT D816V in ≈90-95% of SM patients. Indolent SM (ISM) is the most common SM subtype with various symptoms that can be severe. Advanced SM (AdvSM) has markedly poor prognosis. The advent of KIT inhibitors, targeting mutant KIT and neoplastic MCs, led to a paradigm shift in SM management and markedly improved outcomes. Midostaurin inaugurated the era of KIT inhibitors and was approved for AdvSM in 2017. Avapritinib is the first highly potent and selective inhibitor of KIT D816V that was approved to treat AdvSM and symptomatic ISM (platelets ≥ 50 × 109/L), in the US, in 2021 and 2023, respectively. Pooled analysis of the EXPLORER and PATHFINDER studies, assessing avapritinib in AdvSM, demonstrated rapid and profound reductions (≥ 50%) in markers of MC burden, high response rates (71-75%), and prolonged survival. In the PIONEER study, avapritinib significantly and rapidly improved symptoms/quality of life, and reduced markers of MC burden in ISM patients. The investigational agents bezuclastinib and elenestinib are highly potent and selective inhibitors of KIT D816V with minimal blood-brain barrier penetration. Bezuclastinib reduced markers of MC burden by ≥ 50% in ≈50% of AdvSM patients and ≈90-100% of nonAdvSM patients and reduced symptoms (≥ 50%) in the APEX and SUMMIT studies, respectively. Elenestinib demonstrated dose-dependent efficacy in reducing MC burden markers and improved symptoms in ISM patients in the HARBOR study.

Mast cell activation syndrome: An up-to-date review of literature

Mast cells are a subtype of white blood cells and are involved in the immune system. These cells contain many chemical substances called mediators, which are involved in the allergic response. The fact that mast cells play a role in many events that require urgent intervention, especially anaphylaxis, has led to a more detailed study of these cells. The diseases also caused by dysfunctions of mast cells have been examined in many circumstances. For instance, mast cell activation syndrome is known as an augmented number of cells due to decreased cell death, resulting in clinical symptoms affecting many systems. The main common symptoms include flushing, hypotension, urticaria, angioedema, headache, vomiting and diarrhea. Although the underlying mechanism is not yet clearly known, we aim to review the literature in a broad perspective and bring together the existing knowledge in the light of the literature due to the diversity of its involvement in the body and the fact that it is a little known syndrome.

Mast Cell Activation Syndrome and Gut Dysfunction: Diagnosis and Management

PURPOSE OF REVIEW

Mast cell activation syndrome (MCAS) is a clinical disorder that may explain irritable bowel syndrome (IBS) type symptoms as well as other allergic symptoms experienced by an individual. The diagnosis and treatment of MCAS with specific focus on gastrointestinal (GI) manifestations is reviewed.

RECENT FINDINGS

Although biomarkers for MCAS remain elusive, testing for baseline serum tryptase will distinguish the type of mast cell disorder and urine tests for mast cell mediator metabolites may support the diagnosis. Endoscopy and Colonoscopy with biopsies is not used to diagnose MCAS but is important to rule out other conditions that may cause symptoms. There is increased awareness of the association between MCAS and autonomic dysfunction, small fiber neuropathy, and connective tissue disorders which all impact GI symptoms. MCAS is a disorder often of unknown etiology (idiopathic) and characterized by intermittent allergy type symptoms that affect multiple organ systems after exposure to a trigger. GI symptoms including abdominal cramping and loose stool are prominent and mimic those of IBS. Diagnostic testing is performed to assess for elevations in mast cell mediators during symptoms and to rule out other conditions. A comprehensive treatment plan includes medications that target mast cells, treatments for associated conditions including autonomic dysfunction, and management of comorbid psychiatric illness and nutritional deficits.

Mast Cell-Targeting Therapies in Mast Cell Activation Syndromes

PURPOSE OF REVIEW

Provide an overview of the expanding landscape of mast cell (MC)-targeting treatments in mast cell activation syndromes (MCAS).

RECENT FINDINGS

Tyrosine-kinase inhibitors (TKIs) targeting wild-type and mutated KIT can efficiently induce MC depletion. Avapritinib and midostaurin can also temper IgE-mediated degranulation. Avapritinib has been recently approved by the FDA for the treatment of indolent systemic mastocytosis (ISM). Targeting activation pathways and inhibitory receptors is a promising therapeutic frontier. Recently, the anti Siglec-8 antibody lirentelimab showed promising results in ISM. MCAS is a heterogeneous disorder demanding a personalized therapeutic approach and, especially when presenting as anaphylaxis, has not been formally captured as outcome in prospective clinical trials with TKI. Long-term safety of TKI needs to be addressed. New drugs under investigation in diseases in which non-neoplastic MCs play a pivotal role can provide important inputs to identify new efficient and safe treatments for MCAS.

Cannabidiol Inhibits IgE-Mediated Mast Cell Degranulation and Anaphylaxis in Mice

SCOPE

Cannabidiol (CBD), the most abundant non-psychoactive constituent of the plant Cannabis sativa, is known to possess immune modulatory properties. This study investigates the effects of CBD on mast cell degranulation in human and mouse primary mast cells and passive cutaneous anaphylaxis in mice.

METHODS AND RESULTS

Mouse bone marrow-derived mast cells and human cord-blood derived mast cells are generated. CBD suppressed antigen-stimulated mast cell degranulation in a concentration-dependent manner. Mechanistically, CBD inhibited both the phosphorylation of FcεRI downstream signaling molecules and calcium mobilization in mast cells, while exerting no effect on FcεRI expression and IgE binding to FcεRI. These suppressive effects are preserved in the mast cells that are depleted of type 1 (CB1) and type 2 (CB2) cannabinoid receptors, as well as in the presence of CB1 agonist, CB2 agonist, CB1 inverse agonist, and CB2 inverse agonist. CBD also inhibited the development of mast cells in a long-term culture. The intraperitoneal administration of CBD suppressed passive cutaneous anaphylaxis in mice as evidenced by a reduction in ear swelling and decrease in the number of degranulated mast cells.

CONCLUSION

Based on these results, the administration of CBD is a new therapeutic intervention in mast cell-associated anaphylactic diseases.

Sustained intraoperative allergic reaction to chlorhexidine: A case report

Physicians should be prepared for the presentation and treatment of an anaphylactic reaction in a patient who has been exposed to chlorhexidine perioperatively and consider a sustained source of allergic exposure when faced with a refractory response to treatment.

Combination of H1 and H2 Histamine Receptor Antagonists: Current Knowledge and Perspectives of a Classic Treatment Strategy

Histamine receptor antagonists, which can bind to specific histamine receptors on target cells, exhibit substantial therapeutic efficacy in managing a variety of histamine-mediated disorders. Notably, histamine H1 and H2 receptor antagonists have been extensively investigated and universally acknowledged as recommended treatment agents for numerous allergic diseases and acid-related disorders, respectively. Historically, the combination of H1 and H2 receptor antagonists has been considered a classic treatment strategy, demonstrating relatively superior efficacy compared with single-drug therapies in the treatment of diverse histamine-mediated diseases. The latest emerging studies have additionally suggested the underlying roles of histamine and H1R and H2R in the development of anxiety disorders, arthritic diseases, and postexercise hypotension. Nevertheless, there is still a lack of systematic reviews on the clinical efficacy of combination therapy, greatly limiting our understanding of its clinical application. Here, we present a comprehensive overview of the current knowledge and perspectives regarding the combination of H1 and H2 histamine receptor antagonists in various histamine-mediated disorders. Furthermore, we critically analyze the adverse effects and limitations associated with combination therapy while suggesting potential solutions. Our review can offer a systematic summary and promising insights into the in-depth and effective application of the combination of H1 and H2 receptor antagonists.

Synovial microenvironment-influenced mast cells promote the progression of rheumatoid arthritis

Mast cells are phenotypically and functionally heterogeneous, and their state is possibly controlled by local microenvironment. Therefore, specific analyses are needed to understand whether mast cells function as powerful participants or dispensable bystanders in specific diseases. Here, we show that degranulation of mast cells in inflammatory synovial tissues of patients with rheumatoid arthritis (RA) is induced via MAS-related G protein-coupled receptor X2 (MRGPRX2), and the expression of MHC class II and costimulatory molecules on mast cells are upregulated. Collagen-induced arthritis mice treated with a combination of anti-IL-17A and cromolyn sodium, a mast cell membrane stabilizer, show significantly reduced clinical severity and decreased bone erosion. The findings of the present study suggest that synovial microenvironment-influenced mast cells contribute to disease progression and may provide a further mast cell-targeting therapy for RA.

Mast cell silencing: A novel therapeutic approach for urticaria and other mast cell-mediated diseases

Chronic urticaria (CU) is a mast cell (MC)-dependent disease with limited therapeutic options. Current management strategies are directed at inhibiting IgE-mediated activation of MCs and antagonizing effects of released mediators. Due to the complexity and heterogeneity of CU and other MC diseases and mechanisms of MC activation-including multiple activating receptors and ligands, diverse signaling pathways, and a menagerie of mediators-strategies of MC depletion or MC silencing (i.e., inhibition of MC activation via binding of inhibitory receptors) have been developed to overcome limitations of singularly targeted agents. MC silencers, such as agonist monoclonal antibodies that engage inhibitory receptors (e.g., sialic acid-binding immunoglobulin-like lectin8 -[Siglec-8] [lirentelimab/AK002], Siglec-6 [AK006], and CD200R [LY3454738]), have reached preclinical and clinical stages of development. In this review, we (1) describe the role of MCs in the pathogenesis of CU, highlighting similarities with other MC diseases in disease mechanisms and response to treatment; (2) explore current therapeutic strategies, categorized by nonspecific immunosuppression, targeted inhibition of MC activation or mediators, and targeted modulation of MC activity; and (3) introduce the concept of MC silencing as an emerging strategy that could selectively block activation of MCs without eliciting or exacerbating on- or off-target, immunosuppressive adverse effects.

Systemic mastocytosis: 2023 update on diagnosis and management in adults

INTRODUCTION

Systemic mastocytosis (SM) is a complex and heterogeneous disease, characterized by the clonal accumulation of mast cells in one or more organs. In 2022 both the World Health Organization (WHO) and the International Consensus Classification (ICC) modified the diagnostic and classification criteria of SM. Moreover, the identification of new clinical and molecular variables has improved prognostic tools and led to increasingly individualized therapeutic strategies.

AREAS COVERED

The aim of this review is to present the updates introduced by the International Consensus Classification in diagnostic criteria of SM. In addition, we report the latest data available from the most important clinical trials in patients both with non-advanced and advanced disease, including elenestinib and bezuclastinib.

EXPERT OPINION

Diagnosis and classification of SM has evolved over years. The most recent WHO and ICC classification improved SM diagnostic work-up, providing clinicians with a clear and simplified diagnostic scheme. New approved targeted therapies such as midostaurin and avapritinib modified the treatment paradigm in patients in advanced stage, and next-generation inhibitors actually investigated in clinical trials are expected in the next future.

Management of Advanced Systemic Mastocytosis and Associated Myeloid Neoplasms

Advanced systemic mastocytosis (AdvSM) is a heterogeneous group of disorders characterized by neoplastic mast cell-related organ damage and frequently associated with a myeloid neoplasm. The 3 clinical entities that comprise AdvSM are aggressive SM (ASM), SM-associated hematologic neoplasm, and mast cell leukemia. A gain-of-function KIT D816 V mutation is the primary oncogenic driver found in about 90% of all patients with AdvSM. Midostaurin, an oral multikinase inhibitor with activity against KIT D816V, and avapritinib, an oral selective KIT D816V inhibitor are approved for AdvSM.

Irritable Bowel Syndrome-Like Symptoms in Quiescent Inflammatory Bowel Disease: A Practical Approach to Diagnosis and Treatment of Organic Causes

BACKGROUND

Despite achieving remission in inflammatory bowel disease (IBD), persistent gastrointestinal symptoms are common in quiescent IBD. While irritable bowel syndrome (IBS) is commonly diagnosed in IBD, IBS-like symptoms of recurrent abdominal pain and altered bowel habits can also be attributed to a wide range of overlapping gastrointestinal (GI) etiologies and systemic disorders with GI manifestations that often do not respond to conventional IBS therapies. Delay in diagnosis of these conditions can lead to ongoing patient suffering, reduced quality of life, repetition of invasive testing, increased healthcare utilization, and potentially unnecessary empirical escalation of IBD-related treatments.

AIMS

This review provides a practical approach for the evaluation and diagnosis of IBS mimickers in IBD. We summarize the definition, pathophysiology, diagnosis and treatment of the potential etiologies causing unexplained GI symptoms.

CONCLUSION

Overlapping conditions can co-exist with IBD and explain IBS-like symptoms. The diagnostic work-up in this population should be individualized and tailored to the predominant symptom pattern, associated clinical signs and symptoms and predisposing conditions that can be obtained from a detailed history and physical examination.

Efficacy and anti-inflammatory analysis of glucocorticoid, antihistamine and leukotriene receptor antagonist in the treatment of allergic rhinitis

BACKGROUND

There are many adverse reactions in the treatment of allergic rhinitis (AR) mainly with conventional drugs. Leukotriene receptor antagonists, glucocorticoids and nasal antihistamines can all be used as first-line drugs for AR, but the clinical effects of the three drugs are not clear.

AIM

To examine the impact of glucocorticoids, antihistamines, and leukotriene receptor antagonists on individuals diagnosed with AR, specifically focusing on their influence on serum inflammatory indexes.

METHODS

The present retrospective study focused on the clinical data of 80 patients diagnosed and treated for AR at our hospital between May 2019 and May 2021. The participants were categorized into the control group and the observation group. The control group received leukotriene receptor antagonists, while the observation group was administered glucocorticoids and antihistamines. Conducted an observation and comparison of the symptoms, physical sign scores, adverse reactions, and effects on serum inflammatory indexes in two distinct groups of patients, both before and after treatment.

RESULTS

Subsequent to treatment, the nasal itching score, sneeze score, runny nose score, nasal congestion score, and physical signs score exhibited notable discrepancies (P < 0.05), with the observation group demonstrating superior outcomes compared to the control group (P < 0.05). The interleukin (IL)-6, IL-10, tumor necrosis factor-alpha, Soluble Intercellular Adhesion Molecule-1, Leukotriene D4 after treatment were significantly different and the observation group It is better than the control group, which is statistically significant (P < 0.05). Following the intervention, the incidence of adverse reactions in the observation group, including symptoms such as nasal dryness, discomfort in the throat, bitter taste in the mouth, and minor erosion of the nasal mucosa, was found to be 7.5%. This rate was significantly lower compared to the control group, which reported an incidence of 27.5%. The difference between the two groups was statistically significant (P < 0.05).

CONCLUSION

Glucocorticoids and antihistamines have obvious therapeutic effects, reduce serum inflammatory index levels, relieve symptoms and signs of patients, and promote patients' recovery, which can provide a reference for clinical treatment of AR.

Mastocytosis and related entities: a practical roadmap

Mastocytosis is a complex heterogenous multisystem disorder that is characterized by pathologic activation or accumulation of neoplastic mast cells (MCs) in one or more organs. This clonal MC expansion is often associated with a somatic gain-of-function mutation (D816V in most of the cases) in the KIT gene, encoding for the MC surface receptor KIT (CD117), a stem cell growth factor receptor. Based on clinical and biochemical criteria, the World Health Organization (WHO) divided mastocytosis into different subclasses. The exact prevalence of mastocytosis remains elusive, but it is estimated that the disease affects approximately 1 in 10,000 persons. The clinical presentation of mastocytosis varies significantly, ranging from asymptomatic patients to a life-threatening disease with multiple organ involvement, potentially leading to cytopenia, malabsorption, hepatosplenomegaly, lymphadenopathy, ascites or osteolytic bone lesions with pathological fractures. Patients with mastocytosis may experience symptoms related to release of MC mediators, such as flushing or diarrhea or even more severe symptoms such as anaphylaxis. Recently, a new genetic trait, hereditary alpha tryptasemia (HaT), was described which involves a copy number variation in the TPSAB1-gene. Its role as standalone multisystem syndrome is heavily debated. There is emerging evidence suggesting there might be a link between HaT and due to the increased prevalence of HaT in patients with SM. The aim of this review is to provide a practical roadmap for diagnosis and management of mastocytosis and its associated entities, since there are still many misconceptions about these topics.Abbreviations: AdvSM: Advanced systemic mastocytosis; ASM: Aggressive systemic mastocytosis; aST: acute serum tryptase; BM: Bone marrow; BMM: Bone marrow mastocytosis; bST: baseline serum tryptase; CM: Cutaneous mastocytosis; DCM: Diffuse cutaneous mastocytosis; HVA: Hymenoptera venom allergy; HaT: Hereditary alpha tryptasemia; ISM: Indolent systemic mastocytosis; MC: Mast cell; MCA: Mast cell activation; MCAS: Mast cell activation syndrome; MCL: Mast cell leukemia; MIS: Mastocytosis in the skin; MMAS: Monoclonal mast cell activation syndrome; MPCM: Maculopapular cutaneous mastocytosis; SM: Systemic mastocytosis; SM-AHN: Systemic mastocytosis with associated hematological neoplasm; SSM: Smouldering systemic mastocytosis; VIT: Venom immunotherapy.

Mast Cell Activation Syndrome Update-A Dermatological Perspective

Mast cells (MCs) are infamous for their role in potentially fatal anaphylaxis reactions. In the last two decades, a more complex picture has emerged, as it has become obvious that MCs are much more than just IgE effectors of anaphylaxis. MCs are defenders against a host of infectious and toxic aggressions (their interactions with other components of the immune system are not yet fully understood) and after the insult has ended, MCs continue to play a role in inflammation regulation and tissue repair. Unfortunately, MC involvement in pathology is also significant. Apart from their role in allergies, MCs can proliferate clonally to produce systemic mastocytosis. They have also been implicated in excessive fibrosis, keloid scaring, graft rejection and chronic inflammation, especially at the level of the skin and gut. In recent years, the term MC activation syndrome (MCAS) was proposed to account for symptoms caused by MC activation, and clear diagnostic criteria have been defined. However, not all authors agree with these criteria, as some find them too restrictive, potentially leaving much of the MC-related pathology unaccounted for. Here, we review the current knowledge on the physiological and pathological roles of MCs, with a dermatological emphasis, and discuss the MCAS classification.

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.

Anaphylaxis: Revision of the Brighton collaboration case definition

The Brighton Collaboration (BC) has formulated a number of case definitions which have primarily been applied to adverse events of special interest in the context of vaccine safety surveillance. This is a revision of the 2007 BC case definition for anaphylaxis. Recently, the BC definition has been widely used for evaluating reports of suspected anaphylaxis following COVID-19 vaccination. This has led to debate about the performance of the BC definition in comparison with those from the US National Institute of Allergy and Infectious Disease/Food Allergy Anaphylaxis Network (NIAID/FAAN) and the World Allergy Organization (WAO). BC convened an expert working group to revise the case definition based on their usual process of literature review and expert consensus. This manuscript presents the outcome of this process and proposes a revised case definition for anaphylaxis. Major and minor criteria have been re-evaluated with an emphasis on the reporting of observable clinical signs, rather than subjective symptoms, and a clearer approach to the ascertainment of levels of certainty is provided. The BC case definition has also been aligned with other contemporary and international case definitions for anaphylaxis.

Rare, Overlooked, or Underappreciated Causes of Recurrent Abdominal Pain: A Primer for Gastroenterologists

Recurrent abdominal pain is a common reason for repeated visits to outpatient clinics and emergency departments, reflecting a substantial unmet need for timely and accurate diagnosis. A lack of awareness of some of the rarer causes of recurrent abdominal pain may impede diagnosis and delay effective management. This article identifies some of the key rare but diagnosable causes that are frequently missed by gastroenterologists and provides expert recommendations to support recognition, diagnosis, and management with the ultimate aim of improving patient outcomes.

Successful treatment with Omalizumab of a child affected by Systemic Mastocytosis: clinical and biological implications

BACKGROUND

Pediatric Mastocytosis is a rare and heterogeneous disease, characterized by accumulation of mast cells in the skin (Cutaneous Mastocytosis) and/or, less frequently, in other organs, mainly liver, spleen, bone marrow, lymph nodes and gastrointestinal tract (Systemic Mastocytosis). Patients affected by Systemic Mastocytosis show symptoms caused by  a massive release of mast cell mediators: itching, flushing, abdominal pain, generalized weakness, fatigue and neuropsychiatric disorders. Moreover, children with Systemic Mastocytosis are at greater risk of anaphylactic/anaphylactoid reactions, often poorly controlled by the conventional therapy with antihistamines, mast cells stabilizers and steroids. As a result, children affected by Systemic Mastocytosis have a poor quality of life and suffer the consequence of prolonged steroidal treatment.

CASE PRESENTATION

A child with Systemic Mastocytosis and severe symptoms, refractory to symptomatic and steroidal therapy, has been successfully treated with Omalizumab, an anti-IgE monoclonal antibody usually employed in allergic patients with severe asthma and orticaria. The onset of clinical benefit of Omalizumab therapy was extraordinarily rapid, but proved to be strictly dependent on drug administration. The child has become completely and steadily asymptomatic. No other anaphylactic episodes have been reported. Steroid treatment could be definitively withdrawn after the second dose of Omalizumab, and all the other medications were later reduced. Twenty months after beginning, Omalizumab therapy is still ongoing with good symptomatology control; no side effects have been observed so far.

CONCLUSIONS

In our experience, Omalizumab is an effective treatment for children affected by Systemic Mastocytosis not responding to conventional medical treatments. The main strengths of this therapy are its rapid and extraordinary efficacy to control the severe mast cells mediator-related symptoms, the lack of side effects and its steroid-sparing effect. However, more extensive and controlled studies in pediatric patients affected by Systemic Mastocytosis are needed to substantiate these promising findings.

Removal of Polymer Clips From the Gallbladder Fossa in a Patient With Ehlers-Danlos Syndrome (EDS) to Treat Mast Cell Activation Syndrome (MCAS): A Case Report

Ehlers-Danlos syndrome (EDS) is a group of hereditary disorders characterized by fragility of connective tissue. Clinical manifestations of the disorder involve the skin, joints, blood vessels, and other internal organs. We report the case of a 29-year-old female suffering from EDS and mast cell activation syndrome (MCAS). Her history includes multiple orthopedic surgeries leading to the worsening of her symptoms. This was determined to be due to medical implants placed during her multiple procedures predisposing her to severe immunological reactions. This case report emphasizes the importance of meticulous surgical intervention when managing patients with EDS.

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.

How to evaluate the patient with a suspected mast cell disorder and how/when to manage symptoms

Mast cell disorders include mastocytosis and mast cell activation syndromes. Mastocytosis is a rare clonal disorder of the mast cell, driven by KIT D816V mutation in most cases. Mastocytosis is diagnosed and classified according to World Health Organization criteria. Mast cell activation syndromes encompass a diverse group of disorders and may have clonal or nonclonal etiologies. Hematologists may be consulted to assist in the diagnostic workup and/or management of mast cell disorders. A consult to the hematologist for mast cell disorders may provoke anxiety due to the rare nature of these diseases and the management of nonhematologic mast cell activation symptoms. This article presents recommendations on how to approach the diagnosis and management of patients referred for common clinical scenarios.

Trends and determinants of epinephrine prescriptions: a proxy of anaphylaxis epidemiology?

PURPOSE OF REVIEW

Epinephrine autoinjectors (EAIs) are recommended to all patients previously experiencing anaphylaxis reaction in order to prevent further reactions and fatalities. Under that perspective, EAI prescription could be considered as a proxy of anaphylaxis epidemiology. Nevertheless EAI prescription rates are still unacceptably low.

RECENT FINDINGS

The review focuses on potential determinants, in addition to clinical indications, which might impact EAI prescription rates by exploring the scientific literature published within the past 18 months, wherever available. Although some controversial results, age, sex, ethnicity, geographical setting and socioeconomic conditions might influence both physician prescription behaviour and EAIs' accessibility from the patient's side, which hampers the accuracy of EAI prescription as a proxy of anaphylaxis. Low EAI prescription and refill rates have been recorded even in the absence of significant socioeconomic barriers, suggesting that economical limitations only partially account for the issue, and cultural restrictions have also to be considered and addressed.

SUMMARY

In addition to providing the same opportunities in terms of EAI availability in all countries worldwide, implementing the resources for anaphylaxis management in terms of practical knowledge, education, and allergy specialist networks is an urgent need, even in the absence of socioeconomic barriers.

The Crosstalk between FcεRI and Sphingosine Signaling in Allergic Inflammation

Sphingolipid molecules have recently attracted attention as signaling molecules in allergic inflammation diseases. Sphingosine-1-phosphate (S1P) is synthesized by two isoforms of sphingosine kinases (SPHK 1 and SPHK2) and is known to be involved in various cellular processes. S1P levels reportedly increase in allergic inflammatory diseases, such as asthma and anaphylaxis. FcεRI signaling is necessary for allergic inflammation as it can activate the SPHKs and increase the S1P level; once S1P is secreted, it can bind to the S1P receptors (S1PRs). The role of S1P signaling in various allergic diseases is discussed. Increased levels of S1P are positively associated with asthma and anaphylaxis. S1P can either induce or suppress allergic skin diseases in a context-dependent manner. The crosstalk between FcεRI and S1P/SPHK/S1PRs is discussed. The roles of the microRNAs that regulate the expression of the components of S1P signaling in allergic inflammatory diseases are also discussed. Various reports suggest the role of S1P in FcεRI-mediated mast cell (MC) activation. Thus, S1P/SPHK/S1PRs signaling can be the target for developing anti-allergy drugs.

Patient-reported outcomes among patients with systemic mastocytosis in routine clinical practice: Results of the TouchStone SM Patient Survey

BACKGROUND

Systemic mastocytosis (SM) is a rare clonal neoplasm driven by KIT D816V and other mutations. Data were collected from the patient perspective on disease burden and included an SM-specific symptom assessment tool.

METHODS

US adults aged 18 years and older with a self-reported SM diagnosis completed an online TouchStone SM Patient Survey of 100 items, including the 12-item Short-Form Health Survey, the Indolent Systemic Mastocytosis Symptom Assessment Form, and the Work Productivity and Activity Impairment Questionnaire, as well as questions about SM diagnosis, the impact of SM on daily activities, work impairment, and health care use. The results were analyzed using descriptive statistics.

RESULTS

Fifty-six individuals completed the survey (89% women; median age, 48 years; mean time since diagnosis, 6.7 years), reporting indolent SM (66%), aggressive SM (9%), smoldering SM (5%), and unknown SM subtype (18%). Over a 1-year recall, respondents reported seeking emergency care for anaphylaxis (30%) and taking three or more prescription medications (52%) for SM. Over one half of patients (54%) reduced their work hours because of SM, and 64% avoided leaving home because of symptoms. A majority of respondents (93%) had experienced ≥10 SM-related symptoms, noting that the most bothersome were anaphylactic episodes (18%), abdominal/stomach pain (16%), diarrhea/loose stools (13%), and fatigue (11%). Whereas an Indolent Systemic Mastocytosis Symptom Assessment Form-derived total symptom score of 28 is used to indicate moderate-to-severe symptoms, the mean total symptom score was 52.7. Mental and physical component summary scores from the 12-item Short-Form Health Survey were below population norms.

CONCLUSIONS

Patients who were surveyed reported substantial symptom burden and unmet needs because of SM, as evidenced by seeking emergency care and reporting bothersome symptoms, poor quality of life, and reduced work hours and productivity.

LAY SUMMARY

The objective of this research was to understand the burden and unmet needs in the rare disease of systemic mastocytosis (SM) to guide future care. Fifty-six patients completed an online survey containing questions about their diagnosis, medications, health care use, quality of life, and SM symptoms. The results demonstrated that SM is associated with severe and burdensome symptoms, anaphylactic events, emergency department visits, use of multiple medications, reduced ability to work, and poor physical and psychological quality of life. These findings suggest the need for future advances to address unmet needs in patients affected by SM.

Pathophysiology of Post-COVID syndromes: a new perspective

Most COVID-19 patients recovered with low mortality; however, some patients experienced long-term symptoms described as "long-COVID" or "Post-COVID syndrome" (PCS). Patients may have persisting symptoms for weeks after acute SARS-CoV-2 infection, including dyspnea, fatigue, myalgia, insomnia, cognitive and olfactory disorders. These symptoms may last for months in some patients. PCS may progress in association with the development of mast cell activation syndrome (MCAS), which is a distinct kind of mast cell activation disorder, characterized by hyper-activation of mast cells with inappropriate and excessive release of chemical mediators. COVID-19 survivors, mainly women, and patients with persistent severe fatigue for 10 weeks after recovery with a history of neuropsychiatric disorders are more prone to develop PCS. High D-dimer levels and blood urea nitrogen were observed to be risk factors associated with pulmonary dysfunction in COVID-19 survivors 3 months post-hospital discharge with the development of PCS. PCS has systemic manifestations that resolve with time with no further complications. However, the final outcomes of PCS are chiefly unknown. Persistence of inflammatory reactions, autoimmune mimicry, and reactivation of pathogens together with host microbiome alterations may contribute to the development of PCS. The deregulated release of inflammatory mediators in MCAS produces extraordinary symptoms in patients with PCS. The development of MCAS during the course of SARS-CoV-2 infection is correlated to COVID-19 severity and the development of PCS. Therefore, MCAS is treated by antihistamines, inhibition of synthesis of mediators, inhibition of mediator release, and inhibition of degranulation of mast cells.

Diagnosis and treatment of systemic mastocytosis in Brazil: Recommendations of a multidisciplinary expert panel

INTRODUCTION

Systemic Mastocytosis comprises a group of neoplastic diseases characterized by clonal expansion and infiltration of mast cells into several organs. The diagnosis and treatment of this disease may be challenging for non-specialists.

OBJECTIVE

Make suggestions or recommendations in Systemic Mastocytosis based in a panel of Brazilian specialists.

METHOD AND RESULTS

An online expert panel with 18 multidisciplinary specialists was convened to propose recommendations on the diagnosis and treatment of Systemic Mastocytosis in Brazil. Recommendations were based on discussions of topics and multiple-choice questions and were graded using the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence Chart.

CONCLUSION

Twenty-two recommendations or suggestions were proposed based on a literature review and graded according to the findings.

Hereditary alpha-tryptasemia

PURPOSE OF REVIEW

To discuss our evolving knowledge about the genetic variations in human tryptase and recent advances in associated clinical phenotypes.

RECENT FINDINGS

Hereditary alpha-tryptasemia (HAT) is an autosomal dominant genetic trait and a common cause of elevated basal serum tryptase (BST) in Western populations. It is a risk factor for severe anaphylaxis and an established modifier of mast cell mediator-associated symptoms among patients with systemic mastocytosis (SM).

SUMMARY

The unique properties of naturally occurring alpha/beta-tryptase heterotetramers may explain certain elements of phenotypes associated with HAT. Understanding the physiology of tryptases and how this may relate to the clinical features associated with HAT is the first step in identifying optimal medical management and targets for novel therapeutics.

Clinical challenge for gastroenterologists–Gastrointestinal manifestations of systemic mastocytosis: A comprehensive review

Mastocytosis is a rare and heterogeneous disease characterized by various clinical and biological features that affect different prognoses and treatments. The disease is usually divided into 2 principal categories: cutaneous and systemic disease (SM). Clinical features can be related to mast cell (MC) mediator release or pathological MC infiltration. SM is a disease often hard to identify, and the diagnosis is based on clinical, biological, histological, and molecular criteria with different specialists involved in the patient’s clinical work-up. Among all manifestations of the disease, gastrointestinal (GI) symptoms are common, being present in 14%-85% of patients, and can significantly impair the quality of life. Here we review the data regarding GI involvement in SM, in terms of clinical presentations, histological and endoscopic features, the pathogenesis of GI symptoms, and their treatment.

Nontryptase Urinary and Hematologic Biomarkers of Mast Cell Expansion and Mast Cell Activation: Status 2022

Quantitation of urinary metabolites of histamine, prostaglandin D₂, and leukotriene E₄ can fill the gap in our current efforts to improve diagnosis and management of symptomatic patients with systemic mastocytosis, and/or mast cell activation syndrome, In addition, patients symptomatic due to mast cell activation but who do not meet all the criteria for mast cell activation syndrome can have elevated baseline mediator metabolites. Serum tryptase levels have been the workhorse in diagnosing these disorders, but it has several drawbacks including the need to obtain acute and baseline samples, which require 2 visits to health care facilities and 2 venipunctures. Recently, increased baseline tryptase level has been reported in hereditary alpha tryptasemia, complicating diagnostic possibilities of an increased baseline tryptase level. Furthermore, no treatment can specifically be targeted at tryptase itself. In contrast, the finding of 1 or more elevated urinary levels of histamine, prostaglandin D₂, and/or leukotriene E₄ metabolites (1) greatly narrows diagnostic possibilities for causes of symptoms; (2) informs the practitioner what specific metabolic pathways are involved; and (3) targets the treatment in a specific, direct fashion. As a bonus, baseline spot/random urine samples can be obtained by the patients themselves and repeated at exactly the correct time when symptoms occur.

Global Classification of Mast Cell Activation Disorders: An ICD-10-CM-Adjusted Proposal of the ECNM-AIM Consortium

Mast cell activation (MCA) is common and occurs in a number of pathologic conditions, including IgE-dependent and independent allergic reactions, atopic disorders, autoimmune processes, and mastocytosis. In a subset of patients, no underlying disease and no known trigger of MCA are found. When the symptoms are severe, systemic, and recurrent, and accompanied by a diagnostic increase in the serum tryptase level or other mast cell mediators, an MCA syndrome (MCAS) may be diagnosed. In these patients, the symptoms typically respond to drugs suppressing MCA, mediator production in mast cells, or mediator effects. In each case, diagnostic consensus criteria must be fulfilled to diagnose MCAS. In other patients, MCA may be local, less severe, or less acute, or may be suspected but not confirmed, so that the diagnostic criteria of MCAS are not fulfilled. In these patients, it may be difficult to prove MCA, for example, by measuring multiple mast cell mediators or basophil activation, the latter as a surrogate of IgE-dependent hypersensitivity. However, validated diagnostic criteria for implicating suspected MCA behind such conditions are lacking, even if some of these conditions have recently been assigned to an International Classification of Diseases-10-Clinical Modification code (ICD-10-CM). In this article, we discuss diagnostic features and criteria and propose a ICD-10-CM-adjusted classification for disorders associated with MCA, herein referred to as MCA disorders (MCADs), with special emphasis on the delineation between confirmed MCAS, MCAD not fulfilling MCAS criteria, and suspected MCAD that is not present. In addition, we discuss the discrimination between overt MCAD and predisposing conditions, such as atopic states, mastocytosis, and hereditary alpha tryptasemia.

Mast Cell Diseases in Practice and Research: Issues and Perspectives Raised by Patients and Their Recommendations to the Scientific Community and Beyond

BACKGROUND

Since 2010, patients and physicians have collaborated to understand unmet needs of patients with mast cell diseases, incorporating mastocytosis and mast cell activation disorders, which include mast cell activation syndromes.

OBJECTIVE

This Open Innovation in Science project aims to expand understanding of the needs of patients affected by mast cell diseases, and encourage global communication among patient advocacy groups, physicians, researchers, industry, and government. A major aim is to support the scientific community's efforts to improve diagnosis, management, therapy, and patients' quality of life by addressing unmet needs.

METHODS

In collaboration with mast cell disease specialists, 13 patient advocacy groups from 12 countries and regions developed lists of top patient needs. A core team of leaders from patient advocacy groups collected and analyzed the data and proposed possible actions to address patient needs.

RESULTS

Findings identified similarities and differences among participating countries in unmet needs between patients with mastocytosis and those with mast cell activation syndromes. Issues emphasized struggles relating to the nature and rarity of mast cell diseases, their impact on quality of life, the diagnostic process, access to appropriate care, more effective treatment, and the need for research.

CONCLUSIONS

Solutions vary across countries because situations differ, in particular regarding the existence of and access to centers of excellence and reference centers. Multifaceted mast cell activation syndrome barriers necessitate innovative approaches to improve access to appropriate care. The outcomes of this project should greatly support scientists and clinicians in their efforts to improve diagnosis, management, and treatment of patients with mastocytosis and mast cell activation disorders.

Tyrosine kinase inhibitors for the treatment of indolent systemic mastocytosis: are we there yet?

Indolent systemic mastocytosis (ISM) is the most prevalent form of systemic mastocytosis. Many patients with ISM suffer from mast cell (MC) mediator-related symptoms In a small number of patients, hematologic progression is seen in the follow up. In some patients with ISM, symptoms arising from MC-derived mediators including gastrointestinal symptoms, anaphylaxis, neuropsychiatric symptoms are kept under control with conventional mediator-targeting drugs or MC-stabilizing agents. However, in a substantial number of patients, the symptoms are refractory to such conventional therapy. For these patients, novel drugs and targeted approaches are considered. One reasonable approach may be to apply tyrosine kinase inhibitors directed against KIT and other key kinase targets expressed in neoplastic MC in ISM. Since MC in over 90% of all patients with typical ISM display the KIT D816V mutant receptor, clinically effective KIT-targeting drugs have to be active against this mutant form of KIT. The two such most effective and well-studied agents currently available are midostaurin and avapritinib. Other KIT-targeting drugs, such as imatinib or masitinib, are less effective or even non-effective against KIT D816V and are thus only recommended for use in patients with other KIT mutant forms (non codon 816 mutations) or with wild type KIT. In the present article, we review the current state in the treatment of ISM with tyrosine kinase inhibitors, with special emphasis on treatment responses and potential adverse effects. In fact, all of these agents also have unique and common adverse effects, and their use to treat ISM patients should be balanced against their toxicity and short and long term safety.

Drug-Induced Mast Cell Eradication: A Novel Approach to Treat Mast Cell Activation Disorders?

Mast cell activation is a key event in allergic reactions, other inflammatory states, and mast cell activation syndromes. Mast cell-stabilizing agents, mediator-targeting drugs and drugs interfering with mediator effects are often prescribed in these patients. However, the clinical efficacy of these drugs varies, depending on the numbers of involved mast cells and the underlying pathology. One straightforward approach would be to eradicate the primary target cell. However, to date, no mast cell-eradicating treatment approach has been developed for patients suffering from mast cell activation disorders. Nevertheless, recent data suggest that long-term treatment with agents that effectively inhibit KIT-function results in the virtual eradication of tissue mast cells and a sustained decrease in serum tryptase levels. In many of these patients, mast cell depletion is associated with a substantial improvement in mediator-induced symptoms. In patients with an underlying KIT D816V+ mastocytosis, such mast cell eradication requires an effective inhibitor of KIT D816V, such as avapritinib. However, the use of KIT inhibitors must be balanced against potential side effects. We here discuss mast cell-eradicating strategies in various disease models, the feasibility of this approach, available clinical data, and future prospects for the use of KIT-targeting drugs in mast cell activation disorders.

Personalized Management Strategies in Mast Cell Disorders: ECNM-AIM User's Guide for Daily Clinical Practice

Mastocytosis is a myeloid neoplasm defined by expansion and focal accumulation of clonal mast cells (MCs) in one or more organs. The disease exhibits a complex pathology and may be complicated by MC activation, bone abnormalities, neurological problems, gastrointestinal symptoms, and/or hematologic progression. The World Health Organization divides mastocytosis into cutaneous forms, systemic mastocytosis (SM) and MC sarcoma. In most patients with SM, somatic mutations in KIT are detected. Patients with indolent SM have a normal to near-normal life expectancy, whereas patients with advanced SM, including aggressive SM and MC leukemia, have a poor prognosis. In those with advanced SM, multiple somatic mutations and an associated hematologic neoplasm may be detected. Mediator-related symptoms can occur in any type of mastocytosis. Symptoms may be mild, severe, or even life-threatening. In patients with severe acute symptoms, an MC activation syndrome may be diagnosed. In these patients, relevant comorbidities include IgE-dependent and IgE-independent allergies. Management of patients with SM is an emerging challenge in daily practice and requires in-depth knowledge and a multidisciplinary and personalized approach with selection of appropriate procedures and interventions. In this article, we review the current knowledge on SM and MC activation syndrome, with emphasis on multidisciplinary aspects in diagnosis and patient-specific management. In addition, we provide a user's guide for application of markers, algorithms, prognostic scores, and treatments for use in daily practice.

Experimental Search for New Means of Pathogenetic Therapy COVID-19: Inhibitor of H2-Receptors Famotidine Increases the Effect of Oseltamivir on Survival and Immune Status of Mice Infected by A/PR/8/34 (H1N1)

The development of drugs for the therapy of COVID-19 is one of the main problems of modern physiology, biochemistry and pharmacology. Taking into account the available information on the participation of mast cells and the role of histamine in the pathogenesis of COVID-19, as well as information on the positive role of famotidine in the prevention and treatment of coronavirus infection, an experiment was carried out using famotidine in a mouse model. We used a type A/PR/8/34 (H1N1) virus adapted to mice. The antiviral drug oseltamivir (Tamiflu), which belongs to the group of neuraminidase inhibitors, was used as a reference drug. The use of famotidine in combination with oseltamivir can increase survival, improve the dynamics of animal weight, reduce the level of NKT cells and increase the level of naive T-helpers. Further studies of famotidine in vivo should be aimed at optimizing the regimen of drug use at a higher viral load, as well as with a longer use of famotidine.

COVID-19 Vaccination Safety and Tolerability in Patients Allegedly at High Risk for Immediate Hypersensitivity Reactions

The reported incidence of immediate hypersensitivity reactions (IHR) including anaphylaxis after COVID-19 vaccination is 10-fold higher than for other vaccines. Several patient groups are theorized to be at particular risk. Since specific vaccination guidelines for these patients are based on expert opinion, we performed a retrospective monocentric analysis of the tolerability of adenoviral vector and mRNA-based COVID-19 vaccines in a cohort of patients allegedly at high risk of IHR. Reactions were assessed immediately on-site by allergists during a monitored vaccination protocol and after 3–7 days through telephone interviews. The cohort included 196 patients (aged 12–84 years) with primary mast cell disease (pMCD, 50.5%), idiopathic anaphylaxis (IA, 19.9%), hereditary angioedema (HAE, 5.1%) or miscellaneous indications (24.5%). Twenty-five immediate reactions were observed in 221 vaccine doses (11.3%). Most occurred in IA or miscellaneous patients. None fulfilled anaphylaxis criteria and most were mild and self-limiting. Reaction occurrence was significantly associated with female sex. In total, 13.5% of pMCD patients reported mast cell activation-like symptoms within 72 h post-vaccination. All pediatric pMCD patients (n = 9, 12–18 years) tolerated both mRNA-based vaccine doses. In summary, adenoviral vector and mRNA-based COVID-19 vaccines were safe and well-tolerated in patients with pMCD, HAE, and IA. No anaphylaxis was observed. The mild and subjective nature of most reactions suggests a nocebo effect associated with vaccination in a medicalized setting. Patients with pMCD could experience mild flare-ups of mast cell activation-like symptoms, supporting antihistamine premedication.

Food Allergies and Intolerances: A Clinical Approach to the Diagnosis and Management of Adverse Reactions to Food

Food allergy is an aberrant immunological response to food antigen, which can result in potentially life-threatening reactions. It is often challenging to differentiate food allergy from other adverse reactions to food because their presentations can be indistinguishable. The purpose of this article is to give an overview of the classification, evaluation, and management of adverse food reactions, key differentiating features of food allergy, roles and limitations of various food allergy testing, and promising areas of emerging research. Case studies are used to highlight some of the clinical pearls in diagnosing and managing food-related diseases.

Pediatric Mastocytosis: An Update

Mastocytosis is a rare clonal disorder characterized by excessive proliferation and accumulation of mast cells (MC) in various organs and tissues. Cutaneous mastocytosis (CM), the most common form in children, is defined when MC infiltration is limited to the skin. In adults, the most common form is systemic mastocytosis (SM), characterized by MC proliferation and accumulation in organs, such as bone marrow, lymph nodes, liver, and spleen.1 Genetic aberrations, mainly the KIT D816V mutation, play a crucial role in the pathogenesis of mastocytosis, enhancing MC survival and subsequent accumulation in organs and tissues.2,3 CM includes three forms: solitary mastocytoma, maculopapular cutaneous mastocytosis (MPCM), and diffuse cutaneous mastocytosis (DCM). In most children with CM, skin lesions regress spontaneously around puberty; unfortunately, it is not always a self-limiting disease.4 Even if SM occurs occasionally, all children with mastocytosis require planned follow-up over time. Children with mastocytosis often suffer from MC mediator-related symptoms, the most common of which is itching, often triggered by rubbing the lesions. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers. Treatment with H1 and H2 histamine receptor blockers on demand and the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended.

Role of Mast Cells in the Pathogenesis of Pruritus in Mastocytosis

Pruritus can be defined as an unpleasant sensation that evokes a desire to scratch and significantly impairs patients' quality of life. Pruritus is widely observed in many dermatoses, including mastocytosis, a rare disease characterized by abnormal accumulation of mast cells, which can involve skin, bone marrow, and other organs. Increasing evidence highlights the role of mast cells in neurogenic inflammation and itching. Mast cells release various pruritogenic mediators, initiating subsequent mutual communication with specific nociceptors on sensory nerve fibres. Among important mediators released by mast cells that induce pruritus, one can distinguish histamine, serotonin, proteases, as well as various cytokines. During neuronal-induced inflammation, mast cells may respond to numerous mediators, including neuropeptides, such as substance P, neurokinin A, calcitonin gene-related peptide, endothelin 1, and nerve growth factor. Currently, treatment of pruritus in mastocytosis is focused on alleviating the effects of mediators secreted by mast cells. However, a deeper understanding of the intricacies of the neurobiology of this disease could help to provide better treatment options for patients.

Precision Medicine in Systemic Mastocytosis

Mastocytosis is a rare hematological neoplasm characterized by the proliferation of abnormal clonal mast cells (MCs) in different cutaneous and extracutaneous organs. Its diagnosis is based on well-defined major and minor criteria, including the pathognomonic dense infiltrate of MCs detected in bone marrow (BM), elevated serum tryptase level, abnormal MCs CD25 expression, and the identification of KIT D816V mutation. The World Health Organization (WHO) classification subdivides mastocytosis into a cutaneous form (CM) and five systemic variants (SM), namely indolent/smoldering (ISM/SSM) and advanced SM (AdvSM) including aggressive SM (ASM), SM associated to hematological neoplasms (SM-AHN), and mast cell leukemia (MCL). More than 80% of patients with SM carry a somatic point mutation of KIT at codon 816, which may be targeted by kinase inhibitors. The presence of additional somatic mutations detected by next generation sequencing analysis may impact prognosis and drive treatment strategy, which ranges from symptomatic drugs in indolent forms to kinase-inhibitors active on KIT. Allogeneic stem cell transplant (SCT) may be considered in selected SM cases. Here, we review the clinical, diagnostic, and therapeutic issues of SM, with special emphasis on the translational implications of SM genetics for a precision medicine approach in clinical practice.

Mastocytosis and Mast Cell Activation Disorders: Clearing the Air

Mast cells are derived from hematopoietic stem cell precursors and are essential to the genesis and manifestations of the allergic response. Activation of these cells by allergens leads to degranulation and elaboration of inflammatory mediators, responsible for regulating the acute dramatic inflammatory response seen. Mast cells have also been incriminated in such diverse disorders as malignancy, arthritis, coronary artery disease, and osteoporosis. There has been a recent explosion in our understanding of the mast cell and the associated clinical conditions that affect this cell type. Some mast cell disorders are associated with specific genetic mutations (such as the D816V gain-of-function mutation) with resultant clonal disease. Such disorders include cutaneous mastocytosis, systemic mastocytosis (SM), its variants (indolent/ISM, smoldering/SSM, aggressive systemic mastocytosis/ASM) and clonal (or monoclonal) mast cell activation disorders or syndromes (CMCAS/MMAS). Besides clonal mast cell activations disorders/CMCAS (also referred to as monoclonal mast cell activation syndromes/MMAS), mast cell activation can also occur secondary to allergic, inflammatory, or paraneoplastic disease. Some disorders are idiopathic as their molecular pathogenesis and evolution are unclear. A genetic disorder, referred to as hereditary alpha-tryptasemia (HαT) has also been described recently. This condition has been shown to be associated with increased severity of allergic and anaphylactic reactions and may interact variably with primary and secondary mast cell disease, resulting in complex combined disorders. The role of this review is to clarify the classification of mast cell disorders, point to molecular aspects of mast cell signaling, elucidate underlying genetic defects, and provide approaches to targeted therapies that may benefit such patients.