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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., Competing Interests: Disclosure statement M.C.C. and D.D.M. were supported by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health (NIH). The content is solely the responsibility of the authors and does not represent the official views of the NIH. Disclosure of potential conflict of interest: M. Castells has received research funding and consulting fees from Blueprint Medicines and consulting fees from Cogent Biosciences. M. P. Giannetti has received research funding and consulting fees from Blueprint Medicines and consulting fees from Cogent Biosciences. M. J. Hamilton has received consulting fees from Blueprint Medicines. P. Novak has received funding from Mona Taliaferro/Bay Shore Recycling, the National Heart, Lung, and Blood Institute (NHLNI; 1OT2HL156812-01), and FBRI (2022A018462); is current or previous shareholder of Moderna, Edidas Medicine, Novavax, and Pfizer; and has received royalties from Oxford University Press. J. Nicoloro-SantaBarbara has received consulting fees from Cogent Biosciences and Blueprint Medicines. S. C. Glover received consulting fees from Blueprint Medicine, Janssen, BMS, AbbVie, and Takeda. S. J. Galli has received research funding from and is scientific advisor to Evommune; and is on the scientific advisory board of Jasper Therapeutics. A. White is on the speakers bureau at Blueprint Medicines; and received consulting fees from Cogent Biosciences and Blueprint Medicines. P. Valent received funding from BMS/Celgene and AOP Orphan; and consultancy fees from Novartis, BMS/Celgene, Blueprint, Pfizer, Cogent, and Stemline. J. H. Butterfield has received a fee for the licensing of HMC-1 cell lines. D. D. Metcalfe has received consulting fees from Visterra. J. D. Milner has received consulting fees from Blueprint Medicines. The rest of the authors declare that they have no relevant conflicts of interest., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. All rights reserved.)

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., (© 2022 The Authors. Cancer published by Wiley Periodicals LLC on behalf of American Cancer Society.)

Background: Systemic mastocytosis (SM) is a rare clonal neoplasm driven by the KIT D816V mutation and has a broad range of debilitating symptoms. In this study, the authors evaluated SM disease perceptions and management strategies among US health care providers (HCPs)., Methods: Hematologist/oncologist (H/O) HCPs and allergist/immunologist (A/I) HCPs who were treating four or more patients with SM completed an online, 51-item TouchStone HCP Survey, which queried provider characteristics, perceptions of disease burden, and current management. Descriptive analyses by specialty and SM subtype were performed., Results: Of 304 HCPs contacted, 111 (37%) met eligibility criteria, including 51% A/I specialists and 49% H/O specialists. On average, the HCPs had 14 years of practice experience and cared for 20 patients with SM. A/I HCPs saw more patients with nonadvanced SM (78%) compared with H/O HCPs, who saw similar proportions of patients with nonadvanced SM (54%) and advanced SM (46%). HCPs reported testing 75% of patients for the KIT D816V mutation and found an estimated prevalence of 47%. On average, HCPs estimated 8 months between symptom onset and SM diagnosis. HCPs reported that 62% of patients with indolent SM felt depressed or discouraged because of symptoms. In terms of treatment goals for SM, both types of specialists prioritized symptom improvement for nonadvanced SM and improved survival for advanced SM while also prioritizing improving patient quality of life., Conclusions: Both A/I and H/O specialists highlighted unmet needs for patients with SM. The HCPs surveyed reported a lower rate of KIT D816V mutations and a perceived shorter time between symptom onset and SM diagnosis compared with published estimates., Lay Summary: Specialists treating systemic mastocytosis (SM) completed a 51-item questionnaire about their clinical practices and perceptions of disease impact. The study included 111 hematology, oncology, allergy, and immunology physicians. Physicians reported that most patients had nonadvanced disease, yet SM symptoms significantly disrupted their patients' lives. Physicians estimated that SM is diagnosed within months of symptom onset, in contrast with published reports of years' long delays reported by patients with SM. This study identified unmet needs that can inform educational and patient management priorities in this rare disease., (© 2022 The Authors. Cancer published by Wiley Periodicals LLC on behalf of American Cancer Society.)

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., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Understanding experiences, perceptions, and perspectives of patients with a mast cell disorder (MCD), including cutaneous mastocytosis, systemic mastocytosis, mast cell activation syndromes, and hereditary α-tryptasemia, is an important aspect of successful care, treatment, and informed development of novel therapies. This article reviews existing studies and presents new data on MCD patient perceptions regarding medical care, symptoms, allergies/sensitivities, triggers, future health/disease progression, treatment, impact on daily living, quality of life, support needs, and concerns regarding possible familial disease. Discussion includes aspects affecting the MCD community that require further consideration and development., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)