Pediatric-onset mastocytosis: a long term clinical follow-up and correlation with bone marrow histopathology

Mastocytosis in the skin in dogs: A multicentric case series

Canine cutaneous mastocytosis (CM) is rare in contrast to canine mast cell tumours. In humans, CM commonly affects children and is usually indolent with possible spontaneous resolution. Systemic mastocytosis (SM) with bone marrow involvement typically affects adults, can have a poor outcome, and often includes skin lesions. 'Mastocytosis in the skin' (MIS) is the preferred term of skin lesions, if bone marrow evaluations are not available, which is often the cases in dogs. In human SM and CM, KIT mutations are often detected. The veterinary literature suggests clinical resemblances between human and canine MIS, but data is limited, and KIT mutations are rarely assessed. This retrospective study describes clinicopathological findings, treatment and outcome of 11 dogs with suspected MIS. Dogs with multiple mast cell tumours were excluded. Histopathology reports (n = 5) or slides (n = 6) were reviewed. KIT mutation analysis including exons 8, 9, 11, 14 and 17 were analysed in eight dogs. Median age at diagnosis was 4 years (range, 1-12). Typical clinical signs included multifocal to generalised nodules and papules. Histologically, skin lesions were characterised by dermal infiltration of well-differentiated mast cells. KIT mutations were detected in 3/8 dogs (exon 9: n = 2; exon 11: n = 1). One dog had mastocytaemia suggesting possible SM. Glucocorticoids were mostly successful with lesion improvement in all treated dogs (n = 8). This cohort highlights resemblances between human and canine MIS. Further studies are required to confirm these findings and establish diagnostic criteria for CM and MIS associated with SM in dogs.

Challenges in the Diagnosis of Cutaneous Mastocytosis

BACKGROUND

Mastocytosis is characterized by an accumulation of clonal mast cells (MCs) in tissues such as the skin. Skin lesions in mastocytosis may be clinically subtle or heterogeneous, and giving the correct diagnosis can be difficult.

METHODS

This study compiles personal experiences together with relevant literature, discussing possible obstacles encountered in diagnosing skin involvement in mastocytosis and cutaneous mastocytosis (CM).

RESULTS

The nomenclature of the term "CM" is ambiguous. The WHO classification defines CM as mastocytosis solely present in the skin. However, the term is also used as a morphological description, e.g., in maculopapular cutaneous mastocytosis (MPCM). This is often seen in systemic, as well as cutaneous, mastocytosis. Typical CM manifestations (MPCM), including mastocytoma or diffuse cutaneous mastocytosis (DCM), all share a positive Darier's sign, and can thus be clinically recognized. Nevertheless, distinguishing monomorphic versus polymorphic MPCM may be challenging, even for experienced dermatologists. Less typical clinical presentations, such as MPCM with telangiectatic erythemas (formerly called telangiectasia macularis eruptiva perstans), confluent, nodular or xanthelasmoid variants may require a skin biopsy for histopathological confirmation. Because MC numbers in CM have a large overlap to those in healthy and inflamed skin, detailed histopathological criteria to diagnose mastocytosis in MPCM are needed and have been proposed. D816V KIT mutational analysis in tissue is helpful for confirming the diagnosis. Biomarkers allow the prediction of the course of CM into regression or evolution of the disease. Further diagnostic measures should screen for concomitant diseases, such as malignant melanoma, and for systemic involvement.

CONCLUSIONS

Whereas in typical cases the diagnosis of CM may be uncomplicated, less typical manifestations may require specific investigations for making the diagnosis and predicting its course.

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.

Pediatric and Hereditary Mastocytosis

To a large extent, the clinical picture of pediatric mastocytosis depends on the age at which it is diagnosed. A neonate with diffuse cutaneous mastocytosis may frequently present in a severe state requiring treatment. Toddlers may require long-term anti-mediator therapy, and this may lead to concerns such as organizing preschool education due to the need for epinephrine injections. A teenager may have to face cutaneous disease persistence or a diagnosis of systemic mastocytosis. Further studies are needed to refine the available treatment options and prognosis for different age groups.

Systemic mastocytosis in adults: 2023 update on diagnosis, risk stratification and management

OVERVIEW

Systemic mastocytosis (SM) results from clonal proliferation of mast cells (MC) in extracutaneous organs.

DIAGNOSIS

The major criterion is presence of multifocal MC clusters in the bone marrow and/or extracutaneous organs. Minor diagnostic criteria include elevated serum tryptase level, MC CD25/CD2/CD30 expression, and presence of activating KIT mutations.

RISK STRATIFICATION

Establishing SM subtype as per the International Consensus Classification/World Health Organization classification systems is an important first step. Patients either have indolent/smoldering SM (ISM/SSM) or advanced SM, including aggressive SM (ASM), SM with associated myeloid neoplasm (SM-AMN), and mast cell leukemia. Identification of poor-risk mutations (i.e., ASXL1, RUNX1, SRSF2, NRAS) further refines the risk stratification. Several risk models are available to help assign prognosis in SM patients.

MANAGEMENT

Treatment goals for ISM patients are primarily directed toward anaphylaxis prevention/symptom control/osteoporosis treatment. Patients with advanced SM frequently need MC cytoreductive therapy to reverse disease-related organ dysfunction. Tyrosine kinase inhibitors (TKI) (midostaurin, avapritinib) have changed the treatment landscape in SM. While deep biochemical, histological and molecular responses have been documented with avapritinib treatment, its efficacy as monotherapy against a multimutated AMN disease component in SM-AMN patients remains unclear. Cladribine continues to have a role for MC debulking, whereas interferon-α has a diminishing role in the TKI era. Treatment of SM-AMN primarily targets the AMN component, particularly if an aggressive disease such as acute leukemia is present. Allogeneic stem cell transplant has a role in such patients. Imatinib has a therapeutic role only in the rare patient with an imatinib-sensitive KIT mutation.

Recent advances in diagnosis and therapy in systemic mastocytosis

Mastocytosis is a heterogeneous neoplasm characterized by accumulation of neoplastic mast cells in various organs. There are three main types: cutaneous mastocytosis (CM), systemic mastocytosis (SM), and mast cell sarcoma. CM mainly affects children and is confined to the skin, whereas SM affects adults and is characterized by extracutaneous involvement, with or without cutaneous involvement. Most cases of SM have an indolent clinical course; however, some types of SM have aggressive behavior and a poor prognosis. Recent advances in the understanding of the molecular changes in SM have changed the diagnosis and treatment of aggressive and advanced SM subtypes. The International Consensus Classification and World Health Organization refined the diagnostic criteria and classification of SM as a result of accumulation of clinical experience and advances in molecular diagnostics. Somatic mutations in the KIT gene, most frequently KIT D816V, are detected in 90% of patients with SM. Expression of CD30 and any KIT mutation were introduced as minor diagnostic criteria after the introduction of highly sensitive screening methods. SM has a wide spectrum of clinical features, and only a few drugs are effective at treating advanced SM. Currently, the mainstay of SM treatment is limited to the management of chronic symptoms related to release of mast cell mediators. Small-molecule kinase inhibitors targeting the KIT-downstream and KIT-independent pathways were recently approved for treating advanced SM. I describe recent advances in diagnosis of SM, and review the currently available and emerging therapeutic options for SM management.

Mastocytosis in children: a single-center long-term follow-up study

BACKGROUND

Mastocytosis is a heterogeneous group of rare disorders characterized by the accumulation of clonal mast cells in organs such as the skin and bone marrow. The diagnosis of cutaneous mastocytosis (CM) is based on clinical findings, positive Darier's sign, and histopathology, if necessary.

METHODS

Medical records of 86 children with CM diagnosed during a 35-year long period were reviewed. Most patients (93%) developed CM during the first year of life (median age 3 months). Clinical features at presentation and during the follow-up period were analyzed. Baseline serum tryptase level was measured in 28 patients.

RESULTS

A total of 85% of patients had maculopapular cutaneous mastocytosis/urticaria pigmentosa (MPCM/UP), 9% had mastocytoma, and 6% had diffuse cutaneous mastocytosis (DCM). Boy to girl ratio was 1.1:1. Fifty-four of 86 patients (63%) were followed from 2 to 37 years (median 13 years). Complete resolution was registered in 14% of mastocytoma cases, 14% of MCPM/UP, and in 25% of DCM patients. After the age of 18, skin lesion persisted in 14% mastocytoma, 7% MCPM/UP, and 25% children with DCM. Atopic dermatitis was diagnosed in 9.6% of patients with MPCM/UP. Three of 28 patients had elevated serum tryptase. Prognosis in all patients was good, and there were no signs of progression to systemic mastocytosis (SM).

CONCLUSION

To the best of our knowledge, our results represent the longest single-center follow-up study of childhood-onset CM. We found no complications of massive mast cell degranulation or progression to SM.

Rare gastrointestinal presentation of systemic mastocytosis, a case report

Introduction

Systemic mastocytosis is a rare disease resulting from infiltration of atypical mast cells in multiple organ systems and present with variety of symptoms. Primary appendiceal and cecal mass with isolated abdominal pain as a presenting feature in systemic mastocytosis have not been reported in literature up to now.

Case report

We described a 69- years-old female with systemic mastocytosis who presented with chronic abdominal pain and recent progression. On imaging of the abdomen and pelvis showed a mass in cecum. The patient underwent surgery and histopathologic evaluation of cecal and appendiceal masses revealed uniform small round cell tumor with eosinophilic cytoplasm admixed with many eosinophils distorting normal colonic mucosal architecture. The neoplastic cells showed positive expression of CD117 and Mast cell tryptase. According to all these considerations systemic mastocytosis was confirmed as the diagnosis.

Conclusion

Isolated abdominal pain and primary large intestinal mass are uncommon features of systemic mastocytosis. This case report informed physicians and pathologists to consider it as one of differential diagnosis.

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Mastocytosis is an uncommon neoplastic infiltration of mast cells in one or multiple organs.

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Isolated abdominal pain and primary large intestinal mass are uncommon features of systemic mastocytosis.

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Mastocytosis reveal common surprising clinical signs that to conclude lead to inadequate treatment. mastocytosis.

Histopathological characteristics are instrumental to distinguish monomorphic from polymorphic maculopapular cutaneous mastocytosis in children

Background

Mastocytosis is characterized by the accumulation of mast cells (MCs) in the skin or other organs, and can manifest at any age. A significant number of paediatric mastocytosis cases persist after puberty. In particular, monomorphic maculopapular cutaneous mastocytosis (mMPCM) is often persistent and associated with systemic mastocytosis. However, clinical differentiation of MPCM from polymorphic (p)MPCM can be difficult.

Aim

To identify histopathological features that can help to distinguish mMPCM from other subtypes of paediatric mastocytosis.

Methods

This was a retrospective study using skin biopsies from patients with any subtype of mastocytosis. The localization and density of the MC infiltrate, MC morphology and expression of aberrant markers were evaluated and correlated with clinical characteristics.

Results

In total, 33 biopsies were available for evaluation from 26 children [(10 with mMPCM, 5 with mastocytoma, 3 with diffuse cutaneous mastocytosis (DCM), 8 with pMPCM)] and 7 adults with MPCM. The MC number was increased in all patients, but was higher in children than adults (P < 0.01). The presence of mMPCM was associated with sparing of the papillary dermis from MC infiltration, whereas MC density in the papillary dermis was highest in pMPCM and DCM (P < 0.01). The positive predictive value of the presence of a reticular MC infiltrate for mMPCM was 72.7% (95% CI 51.4–87.0), and the negative predictive value was 83.3% (95% CI 42.2–97.2). There were no relevant differences in the expression of CD2, CD25 or CD30 between the different subtypes.

Conclusion

Skin histopathology might enhance the phenotypical differentiation of mMPCM from other subtypes in children, thereby increasing the accuracy of one's prognosis.

Evaluation and Classification of Mast Cell Disorders: A Difficult to Manage Pathology in Clinical Practice

Mast cells are granulocytic immunomodulatory cells with an important role in physiologic and pathogenic processes due to their location at the junction between the internal and external environment and to their capacity to release a broad range of active mediators. Mast cells mediators have both pro-inflammatory and anti-inflammatory activities and are implicated in various and complex pathology. Mast cells disorders (MCDs) represent a heterogeneous pathology, with frequently difficult and challenging evaluation and diagnostic workup. MCDs can be primary, secondary to other diseases, or idiopathic. Increased research interest in this field was noted during the last decade and various classification criteria, as well as diagnostic and treatment recommendations, were proposed. The aim of this paper is to review the most recent published data on the classification and evaluation of mast cells disorders and to point out the main difficulties in diagnosing and managing these complex diseases in medical practice.

Clinical and Demographic Characteristics of Cutaneous Mastocytosis in Childhood: Single-center Experience

INTRODUCTION

Mastocytosis is a rare and heterogenous disease, and in children it is generally limited to the skin and tends to regress spontaneously in adolescence.

AIM

In this study, demographic, clinical, and laboratory characteristics of pediatric patients with mastocytosis, and also coexisting diseases were investigated.

RESULTS

A total of 61 pediatric patients were included in the study. The male-to-female ratio was 2.2, the median age was 2 years (range, 0.25 to 19 y), and the median follow-up period was 2.0 years (range, 0.25 to 19 y). Types of clinical presentation at diagnosis consisted of mainly urticaria pigmentosa (45.9%). Seven patients were further investigated with suspicion of systemic mastocytosis, they were followed up, median of 9 years (range, 2.5 to 16 y), and none of them developed systemic disease. Coexisting allergic diseases were recorded in total 5 patients (8.2%). Three patients had immunoglobulin A deficiency, 1 patient had elevated immunoglobulin E level. A patient developed mature B-cell lymphoma with a heterozygous mutation in c-KIT exon 11.

DISCUSSION

Cutaneous mastocytosis in children may present as a complex disease with different clinical signs and symptoms. Standardized clinical criteria and guidelines for the follow-up of children with mastocytosis are required.

Establishing diagnostic criteria for mastocytosis in skin biopsies

AIMS

The diagnosis of mastocytosis in skin biopsies can be challenging - particularly in cases with very few mast cells. More diagnostic criteria are needed.

METHODS AND RESULTS

We analyzed 103 skin biopsies from patients with mastocytosis and compared them with biopsies from inflammatory skin lesions and normal skin. Using CD117 immunostaining, we determined the mast cell distribution pattern, the percentage of mast cells in the inflammatory infiltrate, and the mast cell count per mm². We found that a sheet-like or subepidermal distribution of mast cells was specific for mastocytosis. The most significant feature was the percentage of mast cells and not the mast cell count. We found that a mast cell percentage above 40% was fully specific in both adults and children but lacked sensitivity, especially in adults. In children, all cases with a percentage below 40% harbored a number of mast cells above 90 per mm², allowing a straightforward diagnosis. In adults, the diagnosis was more challenging and cases with less than 40% of mast cells could be diagnosed on account of a number of mast cells above 40 per mm², with 88.5% sensitivity and 95.2% specificity. Additional signs might be useful in difficult cases. However, CD25 immunostaining was not useful.

CONCLUSIONS

We confirmed that the criteria currently applied in the bone marrow were not appropriate for the skin. Accordingly, we developed an algorithm for the diagnosis of mastocytosis in skin biopsies with a high level of interrater reproducibility (mean kappa 0.8).

Natural evolution in pediatric cutaneous mastocytosis: 10-year follow-up

BACKGROUND

Mastocytosis is a heterogeneous group of myeloproliferative disorders characterized by accumulation of clonal mast cells in various tissues. The aim of this study was to determine the symptoms evolution and outcome after 10 years observation.

METHODS

Fifty-five children with mastocytosis were included in the study group and monitored concerning mast cell mediator-related symptoms (MC MRSs) and clinical course of the disease for a period of ≥10 years.

RESULTS

Patients presented with a maculopapular cutaneous form of mastocytosis (MPCM) (n = 47) and diffuse cutaneous mastocytosis (DCM) (n = 8). The complete remission (CR) of skin lesions occurred in 10.3% of children after 10 years observation; no remission (NR) was observed in 17.9% children. The CR of skin specific MC MRS occurred in 69.2% children with MPCM and in 14.3% with DCM.

CONCLUSION

Most children with cutaneous mastocytosis (CM) eventually experience a major or partial regression of skin lesions, although complete regression before puberty is rare. The spontaneous remission of skin specific MC MRS is less frequent in children with DCM.

Cutaneous Mastocytosis in Childhood-Update from the Literature

Mastocytosis (M) represents a systemic pathology characterized by increased accumulation and clonal proliferation of mast cells in the skin and/or different organs. Broadly, M is classified into two categories: Cutaneous mastocytosis (CM) and systemic mastocytosis (SM). In children, CM is the most frequent form. Unfortunately, pathogenesis is still unclear. It is thought that genetic factors are involved, but further studies are necessary. As for features of CM, the lesions differ in clinical forms. The most important fact is evaluating a pediatric patient with CM. It must comprise laboratory exams (with baseline dosing of total serum tryptase), a skin biopsy (with a pathological exam and, if the diagnosis is unclear, immunohistochemical tests), and a complete clinical evaluation. It is also defining to distinguish between CM and other diseases with cutaneous involvement. As for the management of CM in children, the first intervention implies eliminating trigger factors. The available cures are oral H1 and/or H2 antihistamines, oral cromolyn sodium, oral methoxypsoralen therapy with long-wave psoralen plus ultraviolet A radiation, potent dermatocorticoid, and calcineurin inhibitors. In children, the prognosis of CM is excellent, especially if the disease's onset is in the first or second years of life.

Systemic mastocytosis in adults: 2021 Update on diagnosis, risk stratification and management

OVERVIEW

Systemic mastocytosis (SM) results from a clonal proliferation of abnormal mast cells (MC) in extra-cutaneous organs.

DIAGNOSIS

The major criterion is presence of multifocal clusters of spindled MC in the bone marrow. Minor diagnostic criteria include elevated serum tryptase level, abnormal MC CD25 expression, and presence of KITD816V mutation.

RISK STRATIFICATION

Establishing SM subtype as per the World Health Organization classification system is an important first step. Broadly, patients either have indolent/smoldering SM (ISM/SSM) or advanced SM, the latter includes aggressive SM (ASM), SM with associated hematological neoplasm (SM-AHN), and mast cell leukemia (MCL). Identification of poor-risk mutations (ie, ASXL1, RUNX1, SRSF2, NRAS) further refines the risk stratification. Recently, clinical and hybrid clinical-molecular risk models have been developed to more accurately assign prognosis in SM patients.

MANAGEMENT

Treatment goals for ISM patients are primarily directed towards anaphylaxis prevention/symptom control/osteoporosis treatment. Patients with advanced SM frequently need MC cytoreductive therapy to ameliorate disease-related organ dysfunction. High response rates have been seen with small-molecule inhibitors that target mutant-KIT, including midostaurin (Food and Drug Administration approved) or avapritinib (investigational). Other options for MC cytoreduction include cladribine or interferon-α, although head-to-head comparisons are lacking. Treatment of SM-AHN primarily targets the AHN component, particularly if an aggressive disease such as acute myeloid leukemia is present. Allogeneic stem cell transplant can be considered in such patients, or in those with relapsed/refractory advanced SM. Imatinib has a limited therapeutic role in SM; effective cytoreduction is limited to those with imatinib-sensitive KIT mutations.

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.

Pediatric Mastocytosis: Recognition and Management

Mastocytosis is a heterogeneous group of disorders characterized by the accumulation of clonal mast cells in organs such as the skin and bone marrow. In contrast to adults, most affected children have only cutaneous involvement. This article reviews the molecular pathogenesis, skin findings, mast cell mediator-related symptoms, evaluation, and management of childhood-onset mastocytosis, noting differences from adult-onset disease. Current classification of cutaneous mastocytosis and the natural histories of different variants in pediatric patients are highlighted, with a focus on clinical manifestations with prognostic implications. A practical algorithm is provided to guide clinical assessment, laboratory and other investigations, and longitudinal monitoring, including recognition of hepatosplenomegaly as a marker of systemic disease and utilization of allele-specific quantitative PCR (ASqPCR) to detect KIT mutations in the peripheral blood. Updated information and consensus-based recommendations regarding possible triggers of mast-cell degranulation (e.g., physical, medications) are discussed, with an emphasis on patient-specific factors and avoiding excessive parental concern. Lastly, an individualized, stepwise approach to treatment of symptoms, skin-directed therapy, and potential use of kinase inhibitors for severe systemic disease is outlined.

Pediatric maculopapular cutaneous mastocytosis: Retrospective review of signs, symptoms, and associated conditions

BACKGROUND/OBJECTIVES

Though maculopapular cutaneous mastocytosis is the most common form of pediatric mastocytosis, it remains unclear which patients will experience severe symptoms. We sought to better define the presentation and the cutaneous and systemic signs and symptoms in patients with maculopapular cutaneous mastocytosis.

METHODS

We analyzed retrospective data on 227 patients diagnosed with maculopapular cutaneous mastocytosis prior to age 15 years from five US clinical sites. We collected data on signs, symptoms, age of onset, and laboratory testing.

RESULTS

Median age of onset of maculopapular cutaneous mastocytosis was 3 months, with 94% of patients presenting prior to age 2 (range 0-15 years). Patients presenting before age 2 had significantly lower serum tryptase level (P = .019). Greater number of skin lesions (P = .006), number of reported skin signs and symptoms (P < .001), and higher tryptase levels (P < .001) were associated with more systemic symptoms.

CONCLUSION

Children with maculopapular cutaneous mastocytosis, who have greater skin involvement, higher serum tryptase level, and more skin signs and symptoms, are more likely to have systemic symptoms.

Hematological Diseases and Osteoporosis

Secondary osteoporosis is a common clinical problem faced by bone specialists, with a higher frequency in men than in women. One of several causes of secondary osteoporosis is hematological disease. There are numerous hematological diseases that can have a deleterious impact on bone health. In the literature, there is an abundance of evidence of bone involvement in patients affected by multiple myeloma, systemic mastocytosis, thalassemia, and hemophilia; some skeletal disorders are also reported in sickle cell disease. Recently, monoclonal gammopathy of undetermined significance appears to increase fracture risk, predominantly in male subjects. The pathogenetic mechanisms responsible for these bone loss effects have not yet been completely clarified. Many soluble factors, in particular cytokines that regulate bone metabolism, appear to play an important role. An integrated approach to these hematological diseases, with the help of a bone specialist, could reduce the bone fracture rate and improve the quality of life of these patients.

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.

Mastocytosis - pathogenesis, clinical manifestation and treatment

The term mastocytosis designates a group of rare disorders characterized by typical skin lesions, frequently associated episodes of anaphylaxis, and clinical symptoms related to the release of various mediators. Dermatologists/allergists are frequently the first to establish the diagnosis. The condition is based on clonal mast cell proliferation, usually in the skin or bone marrow and only rarely in the gastrointestinal tract or other tissues. In general, mastocytosis has a good prognosis in terms of life expectancy. Rare variants - including mast cell leukemia, aggressive mastocytosis, and the exceedingly rare mast cell sarcoma - require cytoreductive therapy. In cases associated with hematological neoplasms, the prognosis depends on the underlying hematologic disorder.

Paediatric mastocytosis: long-term follow-up of 53 patients with whole sequencing of KIT. A prospective study

BACKGROUND

Mastocytosis is a heterogeneous group of clinical disorders characterized by the abnormal accumulation of mast cells. The adult and paediatric forms differ in their clinical and genetic features and outcomes.

OBJECTIVES

To describe the clinical evolution of a well-characterized cohort of paediatric mastocytosis (PM), and to analyse the relationship between KIT mutation and the clinical course.

METHODS

This was a prospective cohort study performed at the National Clinical Reference Center for Mastocytosis. Diagnosis was confirmed by identification of KIT mutation on lesional skin biopsy. Mastocytosis subtype, mast cell mediator-related symptoms (MC MRS) and clinical course were recorded. Fifty-three patients with PM and > 4 years of disease course were enrolled. The mean ± SD age at the final evaluation was 13·2 ± 4·8 years. The main outcome was the type of KIT mutation as a predictor of evolution and clinical characteristics.

RESULTS

Patients presented with maculopapular cutaneous mastocytosis (n = 44), diffuse cutaneous mastocytosis (n = 6) or mastocytoma (n = 3). The mean duration of disease was 12·1 years. Substantial or partial cutaneous regression (18 of 53 and 16 of 53), stabilization or aggravation (16 of 53) and complete cutaneous regression (three of 53) were noted. MC MRS mainly regressed (21 of 53). For 22 patients, evolution of MC MRS and evolution of cutaneous lesions were different. No significant association between evolution and KIT mutation or between evolution and type of cutaneous mastocytosis was found. A late onset of the disease (after 2 years) is associated with worse evolution.

CONCLUSIONS

PM is not systematically self-regressive. MC MRS manifestations and cutaneous lesions can persist or increase overtime. KIT mutation is not a predictor of evolution.

Pediatric Expression of Mast Cell Activation Disorders

Mast cell activation disorders is a term proposed to cover diseases and conditions related to activation of mast cells and effects of mast cell mediators. In its broadest sense, the term encompasses a wide range of diseases from allergic asthma to rhinoconjunctivitis, urticaria, food allergy, anaphylaxis, mastocytosis, and other conditions where MC activation is contributing to the pathogenesis. This article focuses on clinical presentations, challenges, and controversies in pediatric mastocytosis and gives an overview of current knowledge and areas in need of further research.

Cutaneous Mastocytosis in Adults and Children: New Classification and Prognostic Factors

The skin is one of the most frequent tissues affected in patients with mastocytosis, but cutaneous lesions are highly heterogeneous in shape, size, color, number, localization, and distribution. The World Health Organization recognizes 3 subtypes of cutaneous mastocytosis (CM): maculopapular CM (MPCM), diffuse CM, and mastocytoma of skin. An international task force of experts in mastocytosis has recently proposed subdividing MPCM into monomorphic and polymorphic, which could predict the duration of the disease in children. More research is warranted to develop an improved classification of CM that ideally should incorporate robust factors with prognostic impact on disease behavior.

Well-Appearing Newborn With a Vesiculobullous Rash at Birth

A term, appropriate-for-gestational-age, male infant born via normal spontaneous vaginal delivery presented at birth with a full-body erythematous, vesiculobullous rash. He was well-appearing with normal vital signs and hypoglycemia that quickly resolved. His father had a history of herpes labialis. His mother had an episode of herpes zoster during pregnancy and a prolonged rupture of membranes that was adequately treated. The patient underwent a sepsis workup, including 2 attempted but unsuccessful lumbar punctures, and was started on broad-spectrum antibiotics and acyclovir, given concerns about bacterial or viral infection. The rash evolved over the course of several days. Subsequent workup, with particular attention to his history and presentation, led to his diagnosis.

Mastocytosis in Children

PURPOSE OF REVIEW

In this review, we examine the current understanding of the pathogenesis, clinical presentations, diagnostic tools, and treatment options of pediatric mastocytosis as well as the natural history of the disease.

RECENT FINDINGS

We discuss the emerging concept of mast cell activation syndrome. Mastocytosis in children presents most commonly as isolated cutaneous lesions and is a relatively rare occurrence with excellent prognosis and spontaneous regression often occurring by adolescence. Systemic mastocytosis with organ system involvement is a more serious condition and is likely to persist into adulthood.

Pathogenesis and Pathology of Mastocytosis

Systemic mastocytosis is a clonal disorder of mast cells that may variably present with characteristic skin lesions, episodes of mast cell mediator release, and disturbances of hematopoiesis. No curative therapy presently exists. Conventional management has relied on agents that antagonize mediators released by mast cells, inhibit mediator secretion, or modulate mast cell proliferation. Recent advances in the molecular understanding of the pathophysiology of systemic mastocytosis have provided new therapeutic considerations, including new and novel tyrosine kinase inhibitors.

The role of serum tryptase in the diagnosis and monitoring of pediatric mastocytosis: a single-center experience

INTRODUCTION

In children, cutaneous mastocytosis (CM) is considered to be a benign disease associated with mast cell mediator-related symptoms. However, systemic mastocytosis (SM) and anaphylaxis may also occur. Since the basal serum tryptase (bsT) level reflects mast cell burden, its determination is recommended in the diagnosis and follow-up.

AIM

To compare clinical presentation and the course of mastocytosis in children with normal and clearly elevated bsT levels as well as to assess its usefulness in the diagnosis and monitoring of the course of the disease.

MATERIAL AND METHODS

A retrospective analysis of 102 medical records of children with mastocytosis diagnosed and followed-up in the Gdansk Mastocytosis Center in 2014 was performed.

RESULTS

Maculopapular CM (MPCM) was diagnosed in 91 (89.22%) children, diffuse cutaneous mastocytosis (DCM) in 7 (6.86%) and mastocytoma in 4 (3.92%). The presence of flushing and bullous lesions was more frequent in children with bsT levels > 20 ng/ml in comparison with those who had bsT ≤ 20 ng/ml (p = 0.002 and p = 0.03, respectively). Anaphylaxis occurred in 2 MPCM children with bsT levels in normal ranges. In all of the 3 children with persistently and clearly elevated bsT levels, bone marrow biopsy revealed no mast cells infiltrates corresponding to SM.

CONCLUSIONS

Although mastocytosis children with clearly elevated bsT levels frequently develop mediator-related symptoms, the occurrence of anaphylaxis in this age group may be difficult to predict. In pediatric cases with suspected SM, the bsT level is one of the crucial parameters considered before the decision on bone marrow biopsy.

Longitudinal Study of Pediatric Urticaria Pigmentosa

BACKGROUND/OBJECTIVES

Urticaria pigmentosa (UP) is the most common form of mastocytosis in children and is associated with systemic signs, symptoms, and triggers. To our knowledge, the effect of UP on children's quality of life has not been studied. The objective of the current study was to characterize the natural history, triggers, and complications of pediatric UP, identify prognostic indicators, and determine its effect on quality of life.

METHODS

Between 2002 and 2007, children with three or more mastocytomas diagnosed by a pediatric dermatologist were recruited during visits at the Children's Hospital of Wisconsin Dermatology Clinic (Milwaukee, WI). Research visits were conducted every 3 years and telephone interviews yearly. The Children's Dermatology Life Quality Index was administered to subjects 4 years of age and older at enrollment. Laboratory test results were collected for subjects younger than 4 years at enrollment. Subjects were followed until UP resolution or study end in August 2015.

RESULTS

The final cohort size was 43 subjects followed for a median of 8.1 years. Twenty-six subjects were followed through study completion. At age 12 years, 6 patients had disease resolution and 14 remained active. Patients who had disease resolution before age 12 years were more likely to be male and had fewer years of age and smaller lesions, fewer affected areas, and earlier onset. Common medications and anesthetics resulted in no serious reactions. Hymenoptera stings occurred in 51%, with no reports of anaphylaxis. No patient reported a severe effect on quality of life, with most indicating mild to no effect.

CONCLUSION

Severe complications are not common with historically identified triggers. Disease does not resolve before adolescence in most children. UP has a minimal effect on quality of life for most children.

Systemic mastocytosis in adults: 2017 update on diagnosis, risk stratification and management

Disease overview:Systemic mastocytosis (SM) results from a clonal proliferation of abnormal mast cells (MC) in one or more extra-cutaneous organs.

DIAGNOSIS

The major criterion is presence of multifocal clusters of morphologically abnormal MC in the bone marrow. Minor diagnostic criteria include elevated serum tryptase level, abnormal MC expression of CD25 and/or CD2, and presence of KITD816V. Risk stratification: The 2008 World Health Organization (WHO) classification of SM has been shown to be prognostically relevant. Classification of SM patients into indolent (SM), aggressive SM (ASM), SM associated with a clonal non-MC lineage disease (SM-AHNMD) and mast cell leukemia (MCL) subgroups is a useful first step in establishing prognosis.

MANAGEMENT

SM treatment is generally palliative. ISM patients have a normal life expectancy and receive symptom-directed therapy; infrequently, cytoreductive therapy may be indicated for refractory symptoms. ASM patients have disease-related organ dysfunction; interferon-α (±corticosteroids) can control dermatological, hematological, gastrointestinal, skeletal and mediator-release symptoms, but is hampered by poor tolerability. Similarly, cladribine has broad therapeutic activity, with particular utility when rapid MC debulking is indicated; the main toxicity is myelosuppression. Imatinib has a therapeutic role in the presence of an imatinib-sensitive KIT mutation or in KITD816-unmutated patients. Treatment of SM-AHNMD is governed primarily by the non-MC neoplasm; hydroxyurea has modest utility in this setting; there is a role for allogeneic stem cell transplantation in select cases. Investigational drugs: Recent data confirms midostaurin's significant anti-MC activity in patients with advanced SM. Am. J. Hematol. 91:1147-1159, 2016. © 2016 Wiley Periodicals, Inc.

Endocrine manifestations of systemic mastocytosis in bone

Systemic Mastocytosis (SM) is characterized by accumulation of clonal, neoplastic proliferations of abnormal mast cells (MC) in one or more organ system other than skin. Presence of these multifocal clusters of abnormal mast cells is an essential feature of SM. Frequently associated with D816V (KIT) mutation, the presence of this mutation and elevated serum tryptase are minor criteria for diagnosis. SM manifestations depend on the degree of mast cell proliferation, activation and degranulation. SM has a variable prognosis and presentation, from indolent to "smoldering" to life-threatening disease. Bone manifestations of SM include: osteopenia with or without lytic lesions, osteoporosis with or without atraumatic fracture, osteosclerosis with increased bone density, and isolated lytic lesions. Male sex, older age, higher bone resorption markers, lower DKK1 level, lower BMD, absence of urticaria pigmentosa, and alcohol intake are all associated with increased risk of fracture. Treatment of SM is generally palliative. Most therapy is symptom-directed; and, infrequently, chemotherapy for refractory symptoms is indicated. Anti-histamines may alleviate direct bone effects of histamine. Bisphosphonates, including alendronate, clodronate, pamidronate and zoledronic acid are recommended as a first line treatment of SM and osteoporosis. Interferon α may act synergistically with bisphosphonates. As elevation of RANKL and OPG is reported in SM, denosumab could be an effective therapy for bone manifestations of SM.

A child with mastocytosis and lymphomatoid papulosis

A change in clinical behavior of a disease should prompt search for differential diagnoses. Here, the appearance of ulcerated skin nodules in a preexisting cutaneous mastocytosis revealed a concurrent lymphomatoid papulosis – a CD30+ lymphoproliferative skin disease with histological features of a malignant lymphoma, but with a benign self‐healing course.

Mastocytosis: the puzzling clinical spectrum and challenging diagnostic aspects of an enigmatic disease

Mastocytosis is a complex disorder characterized by the accumulation of abnormal mast cells (MC) in the skin, bone marrow and/or other visceral organs. The clinical manifestations result from MC-derived mediators and, less frequently, from destructive infiltration of MCs. Patients suffer from a variety of symptoms including pruritus, flushing and life-threatening anaphylaxis. Whilst mastocytosis is likely to be suspected in a patient with typical skin lesions [i.e. urticaria pigmentosa (UP)], the absence of cutaneous signs does not rule out the diagnosis of this disease. Mastocytosis should be suspected in cases of recurrent, unexplained or severe insect-induced anaphylaxis or symptoms of MC degranulation without true allergy. In rare cases, unexplained osteoporosis or unexplained haematological abnormalities can be underlying feature of mastocytosis, particularly when these conditions are associated with elevated baseline serum tryptase levels. The diagnosis is based on the World Health Organization criteria, in which the tryptase level, histopathological and immunophenotypic evaluation of MCs and molecular analysis are crucial. A somatic KIT mutation, the most common of which is D816V, is usually detectable in MCs and their progenitors. Once a diagnosis of systemic mastocytosis (SM) is made, it is mandatory to assess the burden of the disease, its activity, subtype and prognosis, and the appropriate therapy. Mastocytosis comprises seven different categories that range from indolent forms, such as cutaneous and indolent SM, to progressive forms, such as aggressive SM and MC leukaemia. Although prognosis is good in patients with indolent forms of the disease, patients with advanced categories have a poor prognosis.

Update on Mastocytosis (Part 2): Categories, Prognosis, and Treatment

Mastocytosis is a term used to describe a heterogeneous group of disorders characterized by clonal proliferation of mast cells in different organs. The organ most often affected is the skin. The World Health Organization classifies cutaneous mastocytosis into mastocytoma, maculopapular cutaneous mastocytosis, and diffuse mastocytosis. The systemic variants in this classification are as follows: indolent systemic mastocytosis (SM), aggressive SM, SM with an associated clonal hematological non-mast cell lineage disease, mast cell leukemia, mast cell sarcoma, and extracutaneous mastocytoma. The two latest systemic variants are rare. Although the course of disease is unpredictable in children, lesions generally resolve by early adulthood. In adults, however, the disease tends to persist. The goal of treatment should be to control clinical manifestations caused by the release of mast cell mediators and, in more aggressive forms of the disease, to reduce mast cell burden.

Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology

Cutaneous lesions in patients with mastocytosis are highly heterogeneous and encompass localized and disseminated forms. Although a classification and criteria for cutaneous mastocytosis (CM) have been proposed, there remains a need to better define subforms of cutaneous manifestations in patients with mastocytosis. To address this unmet need, an international task force involving experts from different organizations (including the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology) met several times between 2010 and 2014 to discuss the classification and criteria for diagnosis of cutaneous manifestations in patients with mastocytosis. This article provides the major outcomes of these meetings and a proposal for a revised definition and criteria. In particular, we recommend that the typical maculopapular cutaneous lesions (urticaria pigmentosa) should be subdivided into 2 variants, namely a monomorphic variant with small maculopapular lesions, which is typically seen in adult patients, and a polymorphic variant with larger lesions of variable size and shape, which is typically seen in pediatric patients. Clinical observations suggest that the monomorphic variant, if it develops in children, often persists into adulthood, whereas the polymorphic variant may resolve around puberty. This delineation might have important prognostic implications, and its implementation in diagnostic algorithms and future mastocytosis classifications is recommended. Refinements are also suggested for the diagnostic criteria of CM, removal of telangiectasia macularis eruptiva perstans from the current classification of CM, and removal of the adjunct solitary from the term solitary mastocytoma.

Assessment of clinical findings, tryptase levels, and bone marrow histopathology in the management of pediatric mastocytosis

BACKGROUND

The management of children with pediatric mastocytosis poses a challenge. This is because there is limited information as to the application of clinical and laboratory findings and bone marrow histopathology as they relate to medical intervention and communication.

OBJECTIVE

We sought to examine clinical aspects of pediatric mastocytosis in relationship to serum tryptase levels and bone marrow pathology to provide practical guidance for management.

METHODS

Between 1986 and 2012, 105 children were evaluated at the National Institutes of Health. Organomegaly was confirmed by means of ultrasound. Baseline tryptase levels and at least 1 subsequent tryptase measurement was available in 84 and 37 of these children, respectively. Fifty-three children underwent a bone marrow examination. These data were used to examine relationships between clinical findings, tryptase levels, and marrow histopathology.

RESULTS

In patients with high tryptase levels and severe mediator symptoms, all with organomegaly had systemic disease, and none without organomegaly had systemic disease. Serum tryptase levels differed significantly between patients with urticaria pigmentosa and those with diffuse cutaneous (P < .0001) and systemic mastocytosis (P < .0001) and in all 3 categories versus control subjects (P < .0001). Tryptase levels and symptoms decreased over time in most patients, and tryptase levels correlated with bone marrow mast cell burden in patients with systemic mastocytosis (P < .0001). There was a significant relationship between clinical resolution and the percentage decrease in tryptase levels (P = .0014).

CONCLUSIONS

The majority of children experienced major or complete disease resolution (57%), whereas the remainder exhibited partial improvement. Organomegaly was a strong indicator of systemic disease. Serum tryptase levels furthered classification and reflected clinicopathologic findings, while sequential tryptase measurements were useful in supplementing clinical judgment as to disease course.

Systemic mastocytosis in adults: 2015 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Systemic mastocytosis (SM) results from a clonal proliferation of abnormal mast cells (MC) in one or more extracutaneous organs.

DIAGNOSIS

The major criterion is presence of multifocal clusters of morphologically abnormal MC in the bone marrow. Minor diagnostic criteria include elevated serum tryptase level, abnormal MC expression of CD25 and/or CD2, and presence of KITD816V.

RISK STRATIFICATION

The 2008 World Health Organization classification of SM has been shown to be prognostically relevant. Classification of SM patients into indolent SM (ISM), aggressive SM (ASM), SM associated with a clonal non-MC lineage disease (SM-AHNMD), and mast cell leukemia (MCL) subgroups is a useful first step in establishing prognosis.

MANAGEMENT

SM treatment is generally palliative. ISM patients have a normal life expectancy and receive symptom-directed therapy; infrequently, cytoreductive therapy may be indicated for refractory symptoms. ASM patients have disease-related organ dysfunction; interferon-α (+/-corticosteroids) can control dermatological, hematological, gastrointestinal, skeletal, and mediator-release symptoms, but is hampered by poor tolerability. Similarly, cladribine has broad therapeutic activity, with particular utility when rapid MC debulking is indicated; the main toxicity is myelosuppression. Imatinib has a therapeutic role in the presence of an imatinib-sensitive KIT mutation or in KITD816-unmutated patients. Treatment of SM-AHNMD is governed primarily by the non-MC neoplasm; hydroxyurea has modest utility in this setting; there is a role for allogeneic stem cell transplantation in select cases. Investigational Drugs: Recent data confirms midostaurin's significant anti-MC activity in patients with advanced SM.

Bullous mastocytosis in a 3-month-old infant

Mastocytosis is a rare myeloid neoplasm characterized by abnormal proliferation and accumulation of mast cells in one or more organ systems including the skin, bone marrow, liver, spleen, lymph nodes and gastrointestinal tract. An infant presenting with bullous lesions is an even rarer clinical presentation of cutaneous mastocytosis. The symptoms and complications are mostly in proportion to the mast cell degranulation in tissues. Management is focused on preventing and treating this event. We report a three-month-old infant with bullous mastocytosis to enhance awareness about this rare diagnosis.

Adult mastocytosis: a review of the Santo António Hospital 's experience and an evaluation of World Health Organization criteria for the diagnosis of systemic disease

BACKGROUND

Mastocytosis is a clonal disorder characterized by the accumulation of abnormal mast cells in the skin and/or in extracutaneous organs.

OBJECTIVES

To present all cases of mastocytosis seen in the Porto Hospital Center and evaluate the performance of World Health Organization diagnostic criteria for systemic disease.

METHODS

The cases of twenty-four adult patients with mastocytosis were reviewed. Their clinical and laboratorial characteristics were assessed, and the properties of the criteria used to diagnose systemic mastocytosis were evaluated.

RESULTS

The age of disease onset ranged from 2 to 75 years. Twenty-three patients had cutaneous involvement and 75% were referred by dermatologists. Urticaria pigmentosa was the most common manifestation of the disease. One patient with severe systemic mast cell mediator-related symptoms showed the activating V560G KIT mutation. The bone marrow was examined in 79% of patients, and mast cell immunophenotyping was performed in 67% of the participants. Systemic disease was detected in 84% of cases, and 81% of the sample had elevated serum tryptase levels. All the diagnostic criteria for systemic mastocytosis had high specificity and positive predictive value. Bone marrow biopsy had the lowest sensitivity, negative predictive value and efficiency, while the highest such values were observed for mast cell immunophenotyping. Patients were treated with regimens including antihistamines, sodium cromoglycate, alpha-interferon, hydroxyurea and phototherapy.

CONCLUSIONS

Cutaneous involvement is often seen in adult mastocytosis patients, with most individuals presenting with indolent systemic disease. Although serum tryptase levels are a good indicator of mast cell burden, bone marrow biopsy should also be performed in patients with normal serum tryptase, with flow cytometry being the most adequate method to diagnose systemic disease.

Severity of cutaneous findings predict the presence of systemic symptoms in pediatric maculopapular cutaneous mastocytosis

Although the prognosis of maculopapular cutaneous mastocytosis (MPCM), also referred to as urticaria pigmentosa, is often benign, clinicians lack evidence to reliably predict those at risk of associated systemic manifestations. We sought to elucidate clinical markers of disease severity to provide better treatment and prognostic information for individuals with MPCM. A retrospective chart review querying characteristics of children diagnosed with MPCM in the Emory Dermatology Clinic was performed. Follow-up was obtained through a clinical encounter or telephone interview. Linear regression was used to determine predictors of the number of MPCM-related systemic symptoms. Of 67 subjects, 57% were male, and the mean age of onset was 4.5 months. The maximum number of MPCM lesions was 1 to 10 in 16%, 11 to 30 in 33%, 31 to 50 in 25%, 51 to 100 in 6%, and more than 100 in 20% of subjects. For their MPCM lesions, 46% of subjects reported itching, 34% flushing, and 25% blistering. Reported systemic symptoms included diarrhea (22%), abdominal pain (15%), wheezing or dyspnea (13%), vomiting (10%), bone pain (10%), headaches (8%), cough (10%), rhinorrhea (8%), irritability (6%), and anaphylaxis (1.5%). In a multivariate linear regression analysis, the maximum number of MPCM lesions (p = 0.02) and the number of skin symptoms (p < 0.01) were statistically significant predictors of the number of systemic symptoms, controlling for age of onset, body sites involved, and sex. The correlation between cutaneous findings and symptomatology could aid clinicians in identifying individuals with MPCM who might warrant systemic evaluation and therapy.

Epidemiology of systemic mastocytosis in Denmark

Mastocytosis is a heterogeneous group of diseases characterized by abnormal proliferation of mast cells. Systemic mastocytosis (SM), in which abnormal mast cells are present in tissues beyond the skin, is divided into seven subcategories with varying degrees of severity and prognosis. Very little is known about the epidemiology of SM and its subcategories. This retrospective cohort study of 548 adults with SM diagnosed 1997-2010 was constructed using linked Danish national health registries. The most common subtype of mastocytosis was indolent SM (including urticaria pigmentosa) (n = 450; 82%), followed by SM with subtype unknown (n = 61; 11%), SM with associated clonal haematological non-mast cell lineage disease (n = 24; 4%), aggressive SM (n = 8; 2%), and mast cell leukaemia (n = 5; 1%). The incidence rate for SM (all subtypes including urticaria pigmentosa) was 0·89 per 100 000 per year. Cumulative incidence was 12·46 per 100 000, and the 14-year limited-duration prevalence as of 1 January, 2011 was 9·59 per 100 000. This nationwide cohort from Denmark is the first population-based epidemiological study of mastocytosis. In this cohort of patients aged 15 years and older, SM was found to be overall relatively rare with notable variation by subtype for patient characteristics, survival and epidemiological measures.

Primary mast cell disorders in children

Mastocytosis arises from clonal mast cell expansion and the resultant accumulation of mast cells in cutaneous and sometimes extracutaneous tissues. Recent studies have demonstrated that c-kit mutations seem to be more prevalent in pediatric mastocytosis than previously assumed, but what determines disease evolution and severity in the individual patient remains elusive. For the large majority of children, mastocytosis is a self-limited cutaneous disease that spontaneously regresses before they reach adult age. Rarely, children develop systemic disease progression that is the hallmark of adult-onset disease. Therefore, invasive diagnostic testing, including performing a bone marrow biopsy, is not routinely recommended and usually reserved for children that present with signs of systemic involvement and persistently elevated serum tryptase levels. Despite its often-transient nature and limited skin involvement, some children experience challenging disease-associated symptoms due to spontaneous or trigger-induced mast cell degranulation. Anticipation of and preparation for potential complications can in many instances avoid symptomatic exacerbations. Proper symptomatic treatment and supportive care can often improve the child's quality of life. Cytoreductive therapy is usually not indicated given the natural history of spontaneous disease resolution.