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.

Exploring the Methodological Benefits and Challenges of Utilising a Photovoice Methodology With Individuals in Recovery From Problem Substance Use.

Photovoice is a type of visual research method which supports participants to reflect upon their experiences by capturing digital images. It is a methodology that is routinely used with groups that could be considered vulnerable, as a way of allowing participants to tell their stories for themselves. This article details the process of conducting a Photovoice study with individuals in recovery from problem substance use and reflects on the methodological benefits and challenges of utilising a visual research methodology with this population. Researchers wishing to conduct a Photovoice study with individuals in recovery should be mindful of striking a delicate balance between respecting an individual's autonomy and ensuring their wellbeing. Although ethically complex, Photovoice is an ideal method for research with this population as it allows participants to convey meaning and introduce narratives for themselves in an engaging way.

Defining baseline variability of serum tryptase levels improves accuracy in identifying anaphylaxis.

BACKGROUND: Acute increases of ≥20% + 2 ng/mL (20 + 2 rule) over basal serum tryptase (BST) is the recommended threshold supporting a clinical diagnosis of anaphylaxis. Prospective studies have demonstrated high sensitivity for this algorithm after parenteral exposure, but specificity has not been evaluated. OBJECTIVE: We sought to define a serum tryptase change that distinguishes baseline variability from anaphylaxis on the basis of intraindividual variation in BST. METHODS: Ninety-three total subjects with atopy (n = 62) or hereditary α-tryptasemia (HαT) (n = 31) and ≥2 BST measurements were identified. Sequential BST variability measurements were modeled and threshold ratios that optimized sensitivity and/or specificity determined. Models were tested in 22 individuals with physician-diagnosed anaphylaxis and validated in independent cohorts of individuals with HαT (n = 33), indolent systemic mastocytosis (ISM) (n = 52), and ISM + HαT (n = 12). Mature tryptase levels were measured in HαT (n = 19) and ISM (n = 20). An online application was developed for clinical use. RESULTS: As a result of BST variability, 9.7% (9/93) of primary cohort patients, and 18% (6/33) of HαT, 30% (16/53) of ISM, and 25% (3/12) of ISM + HαT patients from validation cohorts met the 20 + 2 rule despite absent immediate hypersensitivity symptoms; mature tryptase was noncontributory among individuals with HαT or ISM at baseline. A ratio of acute tryptase/BST exceeding 1.685 provided the optimized diagnostic rule for jointly maximizing sensitivity and specificity. Statistically significant improvement in specificity relative to the 20 + 2 rule was observed among individuals with elevated BST caused by HαT and ISM. CONCLUSIONS: Using an acute tryptase/BST ratio of 1.685 improves specificity of measured changes among individuals with HαT and ISM while maintaining high sensitivity for confirmation of anaphylaxis.

Investigating recovery from problem substance use using digital photovoice.

This study investigates the complex process of recovery from problem substance use using a visual research method known as 'Photovoice'. Seven service users from a harm reduction drug service were given digital cameras and asked to photograph 'people, places, and things' meaningful to them in their recovery. These photographs were then used as a catalyst for discussion during two in-depth interviews. This study demonstrates the nuanced experiences of recovery as some participants expressed feeling isolated while others reflected upon their access to various forms of social capital. These findings recognise the link between social capital and recovery outcomes, while also reflecting upon how services might imbed the need for relationship quality within artificial recovery networks. The use of photographs is a novel way of providing voice to the lived experience of service users and adds to the discussion and debate concerning how recovery services may develop.

A widespread blistering eruption: diffuse cutaneous mastocytosis.

Diffuse cutaneous mastocytosis with bullous formation is a rare childhood disease. We report a 5-month-old male who presented with a 3-week history of cutaneous bullae and pruritus. On examination, he had erythema of the cheeks bilaterally and diffuse slightly hyperpigmented, indurated skin on his trunk and abdomen. There were tense vesicles, bullae, and erosions linearly arranged on his trunk and extremities. Both the laboratory and imaging workup were normal. Subsequently, a punch biopsy of a vesicle on the abdomen was obtained and findings confirmed a diagnosis of diffuse cutaneous mastocytosis. An EpiPen(r) was prescribed due to the slightly increased anaphylaxis risk compared to other forms of mastocytosis. There are many purported triggers of diffuse cutaneous mastocytosis and there is currently no known cure which makes management of this disease challenging. This case highlights a rare condition for which official treatment guidelines do not exist. A prompt dermatologic diagnosis is necessary to ensure proper workup and regulation is in place.

Decoding the intricacies of the mast cell compartment.

Historically, understanding of the human mast cell (MC) compartment has lagged behind the appreciation of other cell lineages. MCs exist in vascularised tissues but do not under normal circumstances circulate in blood, and there has been no pharmacological agent identified that totally and selectively inhibits human MC function. There are no substantiated accounts of an apparently healthy individual who is severely lacking in MCs. Thus, some of the approaches employed to understand the function of a specific immune cell are not available to the MC biologist. The disease categories that have provided the greatest insight into MC biology have been monoclonal and IgE-mediated MC disorders. This has led to the categorisation of MC diseases as intrinsic or extrinsic to the MC compartment and to the recognition of the role of mediators in MC activation disorders. Mastocytosis as a clonal disorder not only impacts the MC compartment through changes intrinsic to the MC, but also by the effects of episodes of significant release of MC mediators. The availability of newer therapeutic approaches developed to treat monoclonal MC disorders offer insights into how to more selectively approach management of MC centric diseases.

A randomized double-blind, placebo-controlled study of omalizumab for idiopathic anaphylaxis.

BACKGROUND: Idiopathic anaphylaxis (IA) is a diagnosis of exclusion, thus taking away the option of therapeutic management focused on eliminating the inciting agent. Epinephrine and antihistamines followed by systemic corticosteroids are the mainstays of therapy for acute events. There is no prophylactic therapy that reliably prevents anaphylaxis. OBJECTIVE: We sought to determine the efficacy of omalizumab in the management of patients with frequent episodes of IA in a double-blind, placebo-controlled trial. METHODS: We prospectively enrolled 19 patients with frequent IA (≥6 episodes/y) who then underwent a medical evaluation that included a serum tryptase determination, mutational analysis for KIT D816V, and bone marrow evaluation to rule out a clonal mast cell disorder. Computer-generated random numbers were provided by the study pharmacist. The primary end point was anaphylactic events in the 6 months after baseline. Sixteen patients completed the primary trial. RESULTS: No statistically significant difference was demonstrated between the placebo and treated groups. There was a trend for efficacy in the treatment group, particularly after 60 days. Overall, the safety profile was favorable without long-term side effects. CONCLUSIONS: Omalizumab was safely administered to a difficult-to-treat patient population with IA. The efficacy results trended modestly in favor of the treatment group, but no statistically significant differences were detected.

Heritable risk for severe anaphylaxis associated with increased α-tryptase-encoding germline copy number at TPSAB1.

BACKGROUND: An elevated basal serum tryptase level is associated with severe systemic anaphylaxis, most notably caused by Hymenoptera envenomation. Although clonal mast cell disease is the culprit in some individuals, it does not fully explain this clinical association. OBJECTIVE: Our aim was to determine the prevalence and associated impact of tryptase genotypes on anaphylaxis in humans. METHODS: Cohorts with systemic mastocytosis (SM) and venom as well as idiopathic anaphylaxis from referral centers in Italy, Slovenia, and the United States, underwent tryptase genotyping by droplet digital PCR. Associated anaphylaxis severity (Mueller scale) was subsequently examined. Healthy volunteers and controls with nonatopic disease were recruited and tryptase was genotyped by droplet digital PCR and in silico analysis of genome sequence, respectively. The effects of pooled and recombinant human tryptases, protease activated receptor 2 agonist and antagonist peptides, and a tryptase-neutralizing mAb on human umbilical vein endothelial cell permeability were assayed using a Transwell system. RESULTS: Hereditary α-tryptasemia (HαT)-a genetic trait caused by increased α-tryptase-encoding Tryptase-α/ß1 (TPSAB1) copy number resulting in elevated BST level-was common in healthy individuals (5.6% [n = 7 of 125]) and controls with nonatopic disease (5.3% [n = 21 of 398]). HαT was associated with grade IV venom anaphylaxis (relative risk = 2.0; P < .05) and more prevalent in both idiopathic anaphylaxis (n = 8 of 47; [17%; P = .006]) and SM (n = 10 of 82 [12.2%; P = .03]) relative to the controls. Among patients with SM, concomitant HαT was associated with increased risk for systemic anaphylaxis (relative risk = 9.5; P = .007). In vitro, protease-activated receptor-2-dependent vascular permeability was induced by pooled mature tryptases but not α- or ß-tryptase homotetramers. CONCLUSIONS: Risk for severe anaphylaxis in humans is associated with inherited differences in α-tryptase-encoding copies at TPSAB1.

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

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

Clinical relevance of inherited genetic differences in human tryptases: Hereditary alpha-tryptasemia and beyond.

OBJECTIVE: To describe our current understanding of hereditary α-tryptasemia (HαT), how HαT fits into the evolutionary context of tryptases and contemporary framework of mast cell-associated disorders, and to discuss the future clinical and therapeutic landscape for symptomatic individuals with HαT. DATA SOURCES: Primary peer-reviewed literature. STUDY SELECTIONS: Basic, clinical, and translational studies describing tryptase gene composition, generation, secretion, and elevation and the associated clinical impacts of HαT and treatment of such individuals were reviewed. RESULTS: HαT is a common autosomal dominant genetic trait caused by increased TPSAB1 copy number encoding α-tryptase. Approximately 1 in 20 White individuals have HαT, making it by far the most common cause for elevated basal serum tryptase levels. Although many individuals with HαT may not manifest associated symptoms, the prevalence of HαT is increased in patients with clonal and nonclonal mast cell-associated disorders wherein it is linked to more prevalent and/or severe anaphylaxis and increased mast cell mediator-associated symptoms. Increased generation of mature α/ß-tryptase heterotetramers, and their unique physiochemical properties, may be responsible for some of these clinical findings. CONCLUSION: HαT is a common modifier of mast cell-associated disorders and reactions. Nevertheless, whether HαT may be an independent cause of clinical phenotypes with which it has been associated remains unproven. Correct identification of HαT is critical to accurate interpretation of serum tryptase levels in the clinical evaluation of patients. Beyond HαT, we foresee tryptase genotyping as an important parameter in the standard workup of patients with mast cell-associated disorders and development of therapeutic modalities targeting these patients and associated clinical phenotypes.

Molecular Background, Clinical Features and Management of Pediatric Mastocytosis: Status 2021.

Pediatric mastocytosis is a heterogeneous disease characterized by accumulation of mast cells in the skin and less frequently in other organs. Somatic or germline mutations in the KIT proto-oncogene are detected in most patients. Cutaneous mastocytosis is the most common form of the disease in children. In the majority of cases, skin lesions regress spontaneously around puberty. However, in few patients, mastocytosis is not a self-limiting disease, but persists into adulthood and can show signs of systemic involvement, especially when skin lesions are small-sized and monomorphic. Children with mastocytosis often suffer from mast cell mediator-related symptoms. Severe hypersensitivity reactions can also occur, mostly in patients with extensive skin lesions and blistering. In a substantial number of these cases, the triggering factor of anaphylaxis remains unidentified. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers, treatment with H1 and H2 histamine receptor blockers, and equipment of patients and their families with epinephrine auto-injectors for use in severe anaphylactic reactions. Advanced systemic mastocytosis occurs occasionally. All children with mastocytosis require follow-up examinations. A bone marrow investigation is performed when advanced systemic mastocytosis is suspected and has an impact on therapy or when cutaneous disease persists into adulthood.

Oncogenic D816V-KIT signaling in mast cells causes persistent IL-6 production.

Persistent dysregulation of IL-6 production and signaling have been implicated in the pathology of various cancers. In systemic mastocytosis, increased serum levels of IL-6 associate with disease severity and progression, although the mechanisms involved are not well understood. Since systemic mastocytosis often associates with the presence in hematopoietic cells of a somatic gain-of-function variant in KIT, D816V-KIT, we examined its potential role in IL-6 upregulation. Bone marrow mononuclear cultures from patients with greater D816V allelic burden released increased amounts of IL-6 which correlated with the percentage of mast cells in the cultures. Intracellular IL-6 staining by flow cytometry and immunofluorescence was primarily associated with mast cells and suggested a higher percentage of IL-6 positive mast cells in patients with higher D816V allelic burden. Furthermore, mast cell lines expressing D816V-KIT, but not those expressing normal KIT or other KIT variants, produced constitutively high IL-6 amounts at the message and protein levels. We further demonstrate that aberrant KIT activity and signaling are critical for the induction of IL-6 and involve STAT5 and PI3K pathways but not STAT3 or STAT4. Activation of STAT5A and STAT5B downstream of D816V-KIT was mediated by JAK2 but also by MEK/ERK1/2, which not only promoted STAT5 phosphorylation but also its long-term transcription. Our study thus supports a role for mast cells and D816V-KIT activity in IL-6 dysregulation in mastocytosis and provides insights into the intracellular mechanisms. The findings contribute to a better understanding of the physiopathology of mastocytosis and suggest the importance of therapeutic targeting of these pathways.

Idiopathic anaphylaxis yardstick: Practical recommendations for clinical practice.

Anaphylaxis is considered idiopathic when there is no known trigger. The signs and symptoms of idiopathic anaphylaxis (IA) are identical to those of anaphylaxis because of a known cause and can include cutaneous, circulatory, respiratory, gastrointestinal, and neurologic symptoms. Idiopathic anaphylaxis can be a frustrating disease for patients and health care providers. Episodes are unpredictable, and differential diagnosis is challenging. Current anaphylaxis guidelines have little specific guidance regarding differential diagnosis and long-term management of IA. Therefore, the objective of the Idiopathic Anaphylaxis Yardstick is to use published data and the authors' combined clinical experience to provide practical recommendations for the diagnosis and management of patients with IA.

Adverse reactions to drugs and biologics in patients with clonal mast cell disorders: A Work Group Report of the Mast Cells Disorder Committee, American Academy of Allergy, Asthma & Immunology.

Providers caring for patients with mastocytosis are tasked with the decision to consider therapeutic options. This can come with some trepidation because information available in the public domain lists numerous mast cell (MC) activators based on data that do not discriminate between primates, rodents, and MC lines; do not consider dosage; and do not take into account previous exposure and resultant clinical findings. This being said, there is support in the literature for an enhanced MC response in some patients with mastocytosis and in cases in which there is a greater incidence of adverse reactions associated with certain antigens, such as venoms and drugs. Thus this report provides a comprehensive guide for those providers who must decide on therapeutic options in the management of patients with clonal MC disease.

AAAAI Mast Cell Disorders Committee Work Group Report: Mast cell activation syndrome (MCAS) diagnosis and management.

Our current recommendations for diagnosing and treating primary mast cell (MC) activation syndrome make use of the latest studies and consensus guidelines for clinically recognizing systemic anaphylaxis in real time, regardless of whether allergen-triggered or other pathways are involved; our current understanding of the biomarkers secreted by activated MCs that best discriminate this disorder from other conditions; and the therapeutic drugs that might selectively affect those mediators or MCs themselves. Finding familial or somatic mutations of genes that cause MCs to be hyperactivatable would extend our diagnostic tools and potentially indicate new therapeutic interventions, targeting either the mutated gene product or the associated molecular pathway. In conclusion, we trust that the clinical, laboratory, and therapeutic criteria for primary MC activation syndromes described herein will provide clinicians with practical criteria of sufficient sensitivity and specificity to diagnose most cases without overdiagnosing the disorder in patients who likely have other conditions.

Management of a neonate with diffuse cutaneous mastocytosis: Case report and literature review.

Mastocytosis is an accumulation of clonal mast cells within tissues, commonly caused by mutations in the KIT proto-oncogene. This report describes the management of a neonate with diffuse cutaneous mastocytosis (DCM) caused by a rare activating KIT mutation, specifically internal tandem duplication of the Ala502Tyr503 pair on exon 9, and reviews current data regarding work-up of DCM in pediatric patients.

A distinct biomolecular profile identifies monoclonal mast cell disorders in patients with idiopathic anaphylaxis.

BACKGROUND: Clonal mast cell disorders are known to occur in a subset of patients with systemic reactions to Hymenoptera stings. This observation has prompted the question of whether clonal mast cell disorders also occur in patients with idiopathic anaphylaxis (IA). OBJECTIVE: We sought to determine the prevalence of clonal mast cell disorders among patients with IA, criteria to identify those patients who require a bone marrow biopsy, and whether the pathogenesis of IA involves a hyperresponsive mast cell compartment. METHODS: We prospectively enrolled patients with IA (≥3 episodes/y) who then underwent a medical evaluation that included a serum tryptase determination, allele-specific quantitative PCR (ASqPCR) for the KIT D816V mutation, and a bone marrow examination. Mast cells were cultured from peripheral blood CD34+ cells and examined for releasability after FcεRI aggregation. RESULTS: Clonal mast cell disease was diagnosed in 14% of patients referred with IA. ASqPCR for the KIT D816V mutation was a useful adjunct in helping identify those with systemic mastocytosis but not monoclonal mast cell activation syndrome. A modified overall clonal prediction model was developed by using clinical findings, a serum tryptase determination, and ASqPCR. There was no evidence of a hyperresponsive mast cell phenotype in patients with IA. CONCLUSION: Patients with clonal mast cell disease can present as having IA. Distinct clinical and laboratory features can be used to select those patients more likely to have an underlying clonal mast cell disorder (monoclonal mast cell activation syndrome or systemic mastocytosis) and thus candidates for a bone marrow biopsy.

Political discourse in the hospital heterotopia.

To what extent do we pay attention to the text and images that cover our hospital walls and do we offer any critique either as professionals or service users? In the past we might have expected to see functional or helpful instructions about where to go (or not to go) and in more well-endowed buildings, perhaps we would see some works of art, sculpture, stained glass even, with the intention to encourage, distract or even forewarn us. However, it is now common in UK hospitals, for wall space to be used as a  portal for a range of institutional political messages, that convey information about everything from its own values, behaviours to  advertisements for products and services to requirements for rule following. Michel Foucault's ideas about Heterotopic space can help us to see that hospitals tend to fall (awkwardly) between being a public and personal health care space, and this is a possible explanation for the confused material culture and messages that are shared there. This paper draws on ethnographic methods to reflect on personal experience in order to offer a critique of the contemporary political discourse which has become 'literally' written onto our hospital walls.

Detection of KIT D816V in peripheral blood of children with manifestations of cutaneous mastocytosis suggests systemic disease.

The use of allele-specific quantitative polymerase chain reaction to identify KIT D816V in the peripheral blood of adults with mastocytosis has been reported to have value in the diagnosis, assessment of disease burden and management of this disease. To examine the value of this assay in children with cutaneous manifestations of mastocytosis, we assessed data on 65 patients with all variants of paediatric-onset mastocytosis, including those known to have systemic disease, to correlate KIT mutation status with clinical findings, serum tryptase levels and bone marrow histopathology. We found that KIT D816V was not identified in the peripheral blood of children known to have only cutaneous disease (specificity 100%) but was found in those known to have both cutaneous and systemic/probable systemic disease (sensitivity of 85·2%). These findings were the basis of the development of an algorithm to assist in the decision for when to perform a bone marrow biopsy in children presenting with cutaneous manifestations of mastocytosis.