Bone Marrow Mastocytosis: A Diagnostic Challenge

Altered B-cell, plasma cell, and antibody immune profiles in blood of patients with systemic mastocytosis

BACKGROUND

Systemic mastocytosis (SM) is a heterogeneous disease characterized by an expansion of KIT-mutated constitutively activated mast cells (MCs) that release MC mediators, which might act on the tumor microenvironment including other immune cells.

OBJECTIVE

To investigate the blood distribution of B-cell, plasma cell (PC), and antibody isotype compartments in patients with SM.

METHODS

We used spectral flow cytometry and the EuroFlow Immunomonitoring panel and Lymphocyte Screening Tube to quantify B cells, PCs, and their subsets in blood of 108 patients with SM (35 bone marrow mastocytosis [BMM] cases, 64 indolent SM [ISM] cases, 9 aggressive SM [ASM] cases) versus 117 age-matched healthy donors and paired bone marrow samples of 31 patients with SM versus 17 controls, respectively. In parallel, IgM, IgD, IgG, IgA, and IgE plasma levels were measured.

RESULTS

Compared with healthy donors, patients with SM showed increased immature B-cell production in bone marrow (P = .003) associated with greater release of pre-germinal center immature (P < .001) and naive CD5+ B lymphocytes (P < .001) to blood, but a pronounced decrease in PC counts of all different IgH isotypes and subclasses (P ≤ .001) together with overall increased IgM (P = .001) and IgD (P < .001) plasma levels. Different immune profiles were found per diagnostic subtype of disease with progressively greater counts in blood of immature B lymphocytes together with decreased IgMD+, IgG2+, IgA1+, and IgA2+ memory B cells (P ≤ .032) and elevated IgM (P = .017) plasma levels in cases of ASM, increased IgM (P = .001) and IgD (P = .001) plasma levels in ISM cases, and exacerbated IgE (P < .001) with decreased IgG (P = .008) plasma levels in BMM cases.

CONCLUSIONS

Our results reveal a significant dysregulation of the B-cell and PC compartments in blood of patients with SM, consistent with distinctly altered antibody isotype profiles in plasma of patients with BMM versus ISM versus ASM.

Systemic Mastocytosis: State of the Art

PURPOSE OF REVIEW

Since identification of Systemic mastocytosis (SM) as a distinct disease entity by the World Health Organisation (WHO), there has been a wealth of new research in therapeutic targeting of the pathogenic C-KIT D816V mutation.

RECENT FINDINGS

Avapritinib, the first licensed drug in SM capable of disease modification alongside the increasingly potent, oral and highly selective KIT tyrosine kinase inhibitors (TKIs) Bezuclastinib and now Elenestinib have enabled the prospect of long-term remissions. Studies have shown improved survival and symptomatic control in patients with SM. Of great triumph, this has been achieved in an outpatient setting with apparent tolerable and minimal toxicity. The importance of molecular profiling is being demonstrated in administering combination therapies for SM with an associated haematological neoplasm (AHN), allowing more personalised and streamlined treatment regimes. This review focuses on current management strategies of SM, focusing on state-of-the-art directed therapies, the evidence behind their use with presentation of two clinical cases to highlight key messages.

Underlying systemic mastocytosis in patients with unexplained osteoporosis: score proposal

BACKGROUND

A score to predict the association between unexplained osteoporosis and an underlying systemic Mastocytosis (SM) is lacking.

OBJECTIVE

This study aimed at identifying criteria able to predict the diagnosis of SM without skin involvement and provide an indication for bone marrow (BM) assessment.

METHODS

We included 139 adult patients with unexplained osteoporosis and suspected SM. After BM evaluation, 63 patients (45.3 %) were diagnosed with SM, while the remaining 76 patients (54.7 %) negative for clonal mast cell (MC) disorders, constituted our control group. Univariate and multivariate analysis identified three independent predictive factors: age (<54 years: +1 point, >64 years: -1 point), serum basal tryptase (sBT) levels >19 ng/mL (+2 points) and vertebral fractures (+2 points).

RESULTS

These variables were used to build the OSTEO-score, able to predict the diagnosis of SM before BM assessment with a sensitivity of 73.5 % and a specificity of 67.1 %. Patients with a score < 3 had a lower probability of having SM compared to patients with a score ≥ 3 (28.5 % and 71.4 %, respectively, p < 0.0001). When sBT levels were corrected for the presence of hereditary alpha-tryptasemia (HαT) using the BST calculater (https://bst-calculater.niaid.nih.gov/) recently published [1,2], the sensitivity of ΗαT-adjusted OSTEO-score increased to 87.8 %, and the specificity reached 76.1 %. Also, the positive predictive value of a score ≥ 3 increased to 85.2 %.

CONCLUSIONS

Further studies are needed to validate these results and characterize the role of tryptase genotyping in patients with unexplained osteoporosis in reducing the risk of misdiagnosing patients with SM. Our proposed scoring model allows the identification of patients with the highest probability of having SM, avoiding unnecessary BM studies.

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.

Cognitive, neuropsychiatric and neurological alterations in mastocytosis: A systematic review

BACKGROUND

Mastocytosis manifests with multisystemic symptoms, often involving the nervous system. Numerous cognitive, neuropsychiatric and neurological alterations have been reported in multiple observational studies.

METHODS

We performed a qualitative systematic literature review of reported data consulting the electronic databases Medline, Scopus, Web of Science, Cochrane, and BASE until June 2023.

RESULTS

We selected 24 studies in which the majority showed that a high proportion of mastocytosis patients suffer cognitive, neuropsychiatric and neurological alterations. The most common disorders and estimated ranges of frequency observed in adults were depression (68%-75%), anxiety, high stress or irritability (27%-54%), cognitive impairment (27%-39%, primarily affecting memory skills), and headaches (55%-69%). Attention challenges and learning difficulties were reported in children at a rate of 13%, while neurodevelopmental disorders occurred at rates of 8%-12%. Frequent white abnormalities in mastocytosis patients with concomitant psychocognitive symptoms have been reported although neuroimaging studies have been performed rarely in this population.

CONCLUSION

Further studies with more comprehensive and homogeneous evaluations and neuroimaging and histological analysis should be performed for a better understanding of these manifestations. An earlier detection and proper management of these symptoms could greatly improve the quality of life of these patients.

The diagnostic workup for systemic mastocytosis differs from consensus recommendations: Results of a worldwide survey

Objective

Mastocytosis is a complex disorder affecting various organs. The diagnostic workup can be challenging and requires a multidisciplinary approach including the use of uncommon tests. To assess mastocytosis management around the globe, we conducted the first worldwide online survey for physicians.

Methods

A 21-item questionnaire was sent out to the members of the World Allergy Organization (WAO), the Global Allergy and Asthma European Network (GA2LEN), the Urticaria (UCARE) and Angioedema (ACARE) Centers of Reference and Excellence, the German Society of Allergology and Clinical Immunology (DGAKI), and the European Mast Cell and Basophil Research Network (EMBRN) in April-June 2021.

Results

Across 628 respondents from 79 countries 87.7% and 9.7% of physicians were allergists/clinical immunologists and/or dermatologists. Participating physicians were from all regions of the world (Europe, EU: 41.6%; North America, NA: 24.8%; Latin America, LA: 14.5%; Asia-Pacific, AP: 12.6%; and Africa/Middle East, AME: 6.5%). Only 2.2% of respondents worked at Specialized Mastocytosis Centers (SMCs) in North America or European Union. Physicians reported caring for 4 patients with mastocytosis per year, with higher numbers in European Union and Asia Pacific (5/year) compared to Latin America (2/year). Dermatologists and physicians who work at SMCs reported higher patient numbers (15/year and 80/year, respectively). Suspicion of mastocytosis in the allergology and dermatology community is commonly driven by anaphylaxis (82.9%), mastocytosis skin lesions (82.1%), or elevated tryptase levels (76.6%). Osteoporosis and gastrointestinal symptoms less often prompted suspicion of mastocytosis (21.4% and 49.9%, respectively). World Health Organisation (WHO)-diagnostic criteria and classification, regardless of the region, are only used by about 50% of physicians, with higher rates for SMCs (83.3%). Serum tryptase, bone marrow biopsy, and KIT D816V mutation analysis are included in the diagnostic workup by 90.9%, 61.5%, and 58.4% of physicians, respectively. The biggest challenges for the management of mastocytosis are the lack of more effective treatment options (51.1%), missing multidisciplinary networks (47.1%), and the lack of experience of specialists from other disciplines (39.0%).

Conclusions

The diagnostic workup for mastocytosis differs from consensus recommendations and varies between regions. This may be improved by establishing active multidisciplinary networks, increasing access to diagnostic procedures, consistently applying WHO criteria, and developing new Mastocytosis Centers of Reference and Excellence.

New Insights into the Pathogenesis of Mastocytosis: Emerging Concepts in Diagnosis and Therapy

Mastocytosis is a heterogeneous group of neoplasms defined by a numerical increase and accumulation of clonal mast cells (MCs) in various organ systems. The disease may present as cutaneous mastocytosis or systemic mastocytosis (SM). On the basis of histopathological and molecular features, clinical variables, and organ involvement, SM is divided into indolent SM, smoldering SM, SM with an associated hematologic neoplasm, aggressive SM, and MC leukemia. Each variant is defined by unique diagnostic criteria and a unique spectrum of clinical presentations. A key driver of MC expansion and disease evolution is the oncogenic machinery triggered by mutant forms of KIT. The genetic background, additional somatic mutations, and comorbidities also contribute to the course and prognosis. Patients with SM may also suffer from mediator-related symptoms or even an MC activation syndrome. This article provides an update of concepts on the genetics, etiology, and pathology of mastocytosis, with emphasis on diagnostic criteria and new treatment concepts.

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.

Systemic Mastocytosis and Other Entities Involving Mast Cells: A Practical Review and Update

Evidence in the recent literature suggests that the presentation spectrum of mast cell neoplasms is broad. In this article, we elaborate on recent data pertaining to minor diagnostic criteria of systemic mastocytosis (SM), including sensitive testing methods for detection of activating mutations in the KIT gene or its variants, and adjusted serum tryptase levels in cases with hereditary α-tryptasemia. We also summarize entities that require differential diagnosis, such as the recently reclassified SM subtype named bone marrow mastocytosis, mast cell leukemia (an SM subtype that can be acute or chronic); the rare morphological variant of all SM subtypes known as well-differentiated systemic mastocytosis; the extremely rare myelomastocytic leukemia and its differentiating features from mast cell leukemia; and mast cell activation syndrome. In addition, we provide a concise clinical update of the latest adjusted risk stratification model incorporating genomic data to define prognosis in SM and new treatments that were approved for advanced SM (midostaurin, avapritinib).

Systemic Mastocytosis: Multidisciplinary Approach

Systemic mastocytosis (SM) is a heterogeneous group of diseases that affect almost exclusively adults and are defined by the proliferation and accumulation of clonal mast cells (MC) in various tissues. Disease subtypes range from indolent to rare aggressive forms. Although SM is classified as a rare disease, it is believed to be likely underdiagnosed. Major signs and symptoms mainly depend on MC activation and less frequent organ infiltration, typical of more aggressive variants. Diagnosis may be challenging, and symptoms can be aspecific and involve several organs. Therefore, it is advisable to refer patients to specialized centers, having sufficient knowledge of the disease, sensitive diagnostic procedures, offering a personalized and multidisciplinary diagnostic approach, including at least hematological, allergological, dermatological, and rheumatological evaluations. A precise and timely diagnosis is required for: a) adequate counseling of patients and their physicians; b) beginning of symptomatic treatment (anti-mediator therapy); c) prevention of severe manifestations of the disease (i.e., recurrent anaphylaxis, osteoporosis, and bone fractures); d) cytoreductive treatment of advanced SM variants. This review summarizes the disease's main manifestations and describes the ideal diagnostic approach for adult patients with suspected SM, giving physicians the main notions for correct patient diagnosis and management. This review also highlights the importance of a multidisciplinary approach in this very complex disease.

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.

Frequency and prognostic impact of blood-circulating tumor mast cells in mastocytosis

Circulating tumor mast cells (CTMC) have been identified in the blood of a small number of patients with advanced systemic mastocytosis (SM). However, limited data exists about their frequency and prognostic impact in patients with mast cell activation syndromes (MCAS), cutaneous and non-advanced SM. We investigated the presence of CTMC and mast cell-committed CD34+ precursors in blood of 214 patients with MCAS, cutaneous mastocytosis and SM using highly sensitive next-generation flow cytometry. CTMC were detected at progressively lower counts in almost all advanced SM (96%) and smoldering SM (100%), nearly half (45%) indolent SM cases and few (7%) bone marrow mastocytosis patients, but were systematically absent in cutaneous mastocytosis and MCAS (P<0.0001). In contrast to CTMC counts, the number of mast cell-committed CD34+ precursors progressively decreased from MCAS, cutaneous mastocytosis and bone marrow mastocytosis to indolent SM, smoldering SM and advanced SM (P<0.0001). Clinically, the presence (and number) of CTMC in blood of patients with SM in general and non-advanced SM (indolent SM and bone marrow mastocytosis) in particular was associated with more adverse features of the disease, poorer risk prognostic subgroups as defined by the International Prognostic Scoring System for advanced SM (P<0.0001) and the Global Prognostic Score for mastocytosis (P<0.0001) and a significantly shortened progression-free survival (P<0.0001) and overall survival (P=0.01). Based on our results, CTMC emerge as a novel candidate biomarker of disseminated disease in SM that is strongly associated with advanced SM and poorer prognosis in patients with indolent SM.