Diagnosis and classification of mastocytosis in non-specialized versus reference centres: a Spanish Network on Mastocytosis (REMA) study on 122 patients

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.

Standardized indolent systemic mastocytosis evaluations across a health care system: implications for screening accuracy

ABSTRACT

Timely diagnosis of systemic mastocytosis (SM) remains challenging because of care heterogeneity. We implemented a standardized approach for SM screening and diagnosis using a novel health care system-wide international screening registry. A retrospective analysis assessed rates of SM, cutaneous mastocytosis (CM), and molecular diagnoses before and 2 years after care standardization. The accuracy of individual and combined SM screening tests, basal serum tryptase (BST) ≥11.5 and ≥20.0 ng/mL, REMA ≥2, monomorphic maculopapular CM (MPCM), and elevated BST based upon tryptase genotype, was analyzed. Tryptase genotyping and high-sensitivity KIT p.D816V testing increased substantially 2 years after care standardization. SM diagnoses doubled from 47 to 94, and KIT p.D816V molecular diagnoses increased from 24 to 79. Mean BST and KIT p.D816V variant allele frequency values were significantly lower in patients diagnosed after standardization. Hereditary-alpha tryptasemia prevalence was increased in SM before care standardization (4/30 [13.3%]) but reflected the general population prevalence 2 years later at (5/76 [6.6%]). Elevated BST based upon genotype and BST ≥11.5 ng/mL had the highest sensitivities at 84.2% and 88.3%, respectively. The presence of monomorphic MPCM, elevated BST based upon tryptase genotype, and the combination of REMA ≥2 with elevated BST based upon tryptase genotype had specificities >90%. BST >20.0 ng/mL had low sensitivity and specificity and was not required to establish any indolent SM (ISM) diagnosis. Care standardization increased SM diagnosis rates, particularly in patients with low BSTs. Stratifying BST based upon genotype had the best overall sensitivity and specificity of any ISM screening test and improved the REMA score specificity.

Histopathology and Molecular Genetics in Systemic Mastocytosis: Implications for Clinical Management

The diagnosis of systemic mastocytosis (SM) is based on various clinical, dermatological, serological, and hematological findings but essentially relies on histological evidence of an abnormal increase in tissue-localized mast cells (MCs). The extra-cutaneous organ most frequently affected is the bone marrow (BM), and therefore, histological examination of trephine biopsy specimens of the iliac crest is mandatory on suspicion of SM. At microscopic examination, neoplastic MCs show aberrant morphology, usually with prominent spindling. Immunohistochemistry is a useful tool in the diagnosis of SM because mast cell (MC) infiltrates may be slight and scarce, in a mixed background of lymphohistiocytic cells, eosinophils, and plasma cells. Moreover, neoplastic MCs exhibit an aberrant phenotype. Recent evidence, largely derived from molecular genetics, has enhanced the diagnostic capability of SM, also providing the basis for adequate prognostic and therapeutic evaluation. The cases herein reported illustrate the variable clinical manifestations and disease course of SM, focusing on diagnostic and therapeutic challenges. In accordance with the World Health Organization (WHO) classification and the International Consensus Classification (ICC) systems, our findings emphasize the importance of an integrated diagnostic approach for SM, with proper application of diverse assessment methodologies in order to improve SM classification and treatment effectiveness.

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.

Fatal hymenoptera venom anaphylaxis by undetected clonal mast cell disorder: A better identification of high risk patients is needed

Hymenoptera venom anaphylaxis is the most frequent cause of anaphylaxis and responsible for about 20% of all fatal anaphylaxis cases in adults. We report two cases of fatal hymenoptera venom anaphylaxis with undiagnosed underlying mastocytosis and review the risk factors for severe or fatal hymenoptera venom anaphylaxis, as well as the specificities of its association with mastocytosis. As hymenoptera venom allergic patients with underlying clonal mast cell disorder generally lack typical skin lesions of mastocytosis, its diagnosis can easily be missed, underscoring the importance and need for diagnostic strategies in order to correctly identify these patients. Predominant cardiovascular symptoms in the absence of urticaria or angioedema following an insect sting are suggestive of underlying clonal mast cell disorder, and should be distinguished from panic attack or vasovagal syncope. Similarly, an unexplained syncope or an "idiopathic" anaphylaxis might reveal mastocytosis or hereditary alpha-tryptasemia. Acute and basal serum tryptase measurements should always be integrated in the diagnostic work-up of an insect sting reaction or unexplained syncope or shock of any origin.

PATHOGENIC AND DIAGNOSTIC RELEVANCE OF KIT IN PRIMARY MAST CELL ACTIVATION DISORDERS

OBJECTIVE

Mast cell (MC) activation (MCA) defines the mechanism by which certain patients suffer from symptoms due to the effect of a wide range of mediators released from MC upon their activation triggered by different stimuli. When these symptoms are severe and recurrent, the diagnosis of MCA syndrome (MCAS) might be considered. Here we review the relevant aspects related to the pathogenesis of MCAS, with special emphasis on the prevalence and diagnostic relevance of KIT mutations.

DATA SOURCES

PubMed was searched between 1980 and 2021 using the following terms: Mast cell activation syndromes, mast cell activation, anaphylaxis, KIT mutations, KIT D816V, indolent systemic mastocytosis, bone marrow mastocytosis, cutaneous mastocytosis, IgE anaphylaxis and idiopathic anaphylaxis.

STUDY SELECTIONS

Only articles published in English were selected based on their relevance to MCAS and/or severe and recurrent anaphylaxis.

RESULTS

MCAS can be classified in clonal MCAS and non-clonal MCAS depending on the presence vs. absence of an underlying KIT mutation (mostly KIT D816V), respectively. In contrast to clonal MCAS in which MCA is associated with a primary MC disorder (i.e. primary MCAS) such as mastocytosis or monoclonal MCAS, non-clonal MCAS can be secondary to known or unidentified triggers (i.e. secondary and idiopathic MCAS, respectively).

CONCLUSION

The clinical heterogeneity and complexity of the molecular assays needed for the study of MCAS patients might lead to misdiagnosis, particularly when patients are evaluated at non-specialized centers. Thus, referral of patients suffering from clinical manifestations suggestive of MCAS to Reference Centers on mastocytosis and MC diseases is strongly recommended.

Case Report: Mastocytosis: The Long Road to Diagnosis

Mastocytosis is a heterogeneous group of disorders characterized by expansion and accumulation of clonal mast cells. Patients mainly present with either cutaneous lesions, anaphylaxis, or both. Its low prevalence and unusual features often hinder its diagnosis for several years. We report the case of an 18-year-old male who was referred to our department with a long-standing history of atypical skin lesions, allergic rhinitis, exercise-induced bronchoconstriction and what was believed to be food-related flushing and anaphylaxis, that was later diagnosed with mastocytosis. This case illustrates the need to consider investigating for mastocytosis when recurrent anaphylaxis is present, especially in the presence of atypical skin lesions, even if normal serum basal tryptase levels and allergic sensitization are present.

The Italian Mastocytosis Registry: 6-year experience from a hospital-based registry

Aim: We collected ‘real-life’ data on the management of patients with mastocytosis in the Italian Mastocytosis Registry. Methods: Six hundred patients diagnosed with mastocytosis between 1974 and 2014 were included from 19 centers. Results: Among adults (n = 401); 156 (38.9%) patients were diagnosed with systemic mastocytosis. In 212 adults, no bone marrow studies were performed resulting in a provisional diagnosis of mastocytosis of the skin. This diagnosis was most frequently established in nonhematologic centers. In total, 182/184 pediatric patients had cutaneous mastocytosis. We confirmed that in the most patients with systemic mastocytosis, serum tryptase levels were >20 ng/ml and KIT D816V was detectable. Conclusion: The Italian Mastocytosis Registry revealed some center-specific approaches for diagnosis and therapy. Epidemiological evidence on this condition is provided.

Bone Marrow Expression of Mast Cell Disorders

Mast cell disorders comprise a heterogeneous group of rare diseases, the diagnosis of which still remains a challenge. Bone marrow analysis constitutes the most appropriate site for screening systemic involvement in mastocytosis. Morphologic, immunohistochemical, flow cytometric immunophenotyping, and molecular studies should be routinely performed for diagnostic/prognostic purposes in experienced reference centers during the diagnostic workup in suspected systemic mastocytosis. The authors review the most relevant characteristics of bone marrow expression of mast cell disorders as well as the different methodological approaches to be applied to perform an objective and reproducible diagnosis and classification of mastocytosis and other mast cell disorders.

Advances in the understanding and clinical management of mastocytosis and clonal mast cell activation syndromes

Clonal mast cell activation syndromes and indolent systemic mastocytosis without skin involvement are two emerging entities that sometimes might be clinically difficult to distinguish, and they involve a great challenge for the physician from both a diagnostic and a therapeutic point of view. Furthermore, final diagnosis of both entities requires a bone marrow study; it is recommended that this be done in reference centers. In this article, we address the current consensus and guidelines for the suspicion, diagnosis, classification, treatment, and management of these two entities.

A unique presentation of pulmonary disease in advanced systemic mastocytosis, proven by the presence of mast cells in bronchoalveolar lavage: a case report

BACKGROUND

Systemic mastocytosis is a rare myeloproliferative disease characterized by the uncontrolled proliferation of aberrant mast cells. It has varying clinical manifestations. For unknown reasons, pulmonary localization of mastocytosis is extremely rare.

CASE PRESENTATION

In this report, we describe a case of a young Caucasian female with systemic mastocytosis who had an associated hematological non-mast-cell lineage disease with pulmonary interstitial disease directly related to her mastocytosis. The diagnosis was proven by the presence of mast cells in bronchoalveolar lavage. The treatment of her associated hematological disease (myelofibrosis with myelodysplasia) was hampered by rapidly declining pulmonary function and progressive organ dysfunction due to aggressive systemic mastocytosis. She died approximately 1 year after the diagnosis.

CONCLUSIONS

To our knowledge, this is the first case in which mast cells were detected in bronchoalveolar lavage. Moreover, to date, only two other cases of pulmonary interstitial disease due to mastocytosis have been published. Juggling therapies for systemic mastocytosis and myelofibrosis is very difficult; however, aggressive therapy for both diseases is essential to give these patients a chance to survive.

Definition, aims, and implementation of GA(2) LEN Urticaria Centers of Reference and Excellence

BACKGROUND

GA²LEN, the Global Allergy and Asthma European Network, has recently launched a program for the development, interaction, and accreditation of centers of reference and excellence in special areas of allergy embedded in its overall quality management of allergy centers of excellence. The first area chosen is urticaria. Urticaria is a common and debilitating condition and can be a challenge for both patients and treating physicians, especially when chronic. Centers of reference and excellence in urticaria (UCAREs) can help to improve the management of hard-to-treat conditions such as urticaria.

AIMS

Here, we describe the aims, the requirements and deliverables, the application process, and the audit and accreditation protocol for GA²LEN UCAREs.

RESULTS

The main aims of GA²LEN UCAREs are to provide excellence in urticaria management, to increase the knowledge of urticaria by research and education, and to promote the awareness of urticaria by advocacy activities. To become a certified GA²LEN UCARE, urticaria centers have to apply and fulfill 32 requirements, defined by specific deliverables that are assessed during an audit visit.

DISCUSSION AND CONCLUSION

The GA²LEN UCARE program will result in a strong network of urticaria specialists, promote urticaria research, and harmonize and improve urticaria management globally.

Impact of centralized evaluation of bone marrow histology in systemic mastocytosis

BACKGROUND

Bone marrow (BM) histology/immunohistochemistry, KIT D816V mutation analysis and serum tryptase measurements are mandatory tools for diagnosis of systemic mastocytosis (SM).

MATERIALS AND METHODS

Within the 'German Registry of Disorders on Eosinophils and Mast Cells', we identified 65 patients with SM who had two consecutive BM biopsies. The first biopsy was evaluated by a local pathologist (LP) and the second biopsy by a reference pathologist (RP) of the 'European Competence Network on Mastocytosis (ECNM)'.

RESULTS

Final diagnoses by RP were SM (n = 27), SM or aggressive SM (ASM) with associated clonal haematological non-mast cell lineage disease [(A)SM-AHNMD, n = 34)] or mast cell leukaemia ± AHNMD (n = 4). In 15 of 65 patients (23%), initial diagnoses by LP were incorrect (by overlooking SM), for example primary myelofibrosis (n = 3), myelodysplastic/myeloproliferative neoplasm unclassified (n = 3) or B-cell lymphoma (n = 2). Fourteen of 15 patients (93%) with incorrect diagnosis had an advanced SM, mostly (A)SM-AHNMD. In the 50 concordantly diagnosed patients, immunohistochemical markers for quantitative assessment of mast cell infiltration, for example CD117 (KIT) or CD25, were applied by LP in only 34 of 50 patients (68%), and mutational analysis for KIT D816V was performed or recommended in only 13 of 50 patients (26%). Finally, the subclassification of SM was discordant because LP did not diagnose AHNMD in nine of 50 (18%) patients.

CONCLUSIONS

In summary, adequate diagnosis and subclassification of SM requires an in-depth evaluation of the BM by experienced haematopathologists (preferably in a reference centre) in combination with molecular genetics, serum tryptase level and clinical parameters.