Phenotypic and genotypic characteristics of mastocytosis according to the age of onset

Poor Applicability of Currently Available Prognostic Scoring Systems for Prediction of Outcome in KIT D816V-Negative Advanced Systemic Mastocytosis

Within our nationwide registry, we identified a KIT D816V mutation (KIT D816Vpos.) in 280/299 (94%) patients with advanced systemic mastocytosis (AdvSM). Age, cytopenias and the presence of additional somatic mutations confer inferior overall survival (OS). However, little is known about the characteristics of KIT D816V-negative (D816Vneg.) AdvSM. In 19 D816Vneg. patients, a combination of clinical, morphological and genetic features revealed three subgroups: (a) KIT D816H- or Y-positive SM (KIT D816H/Ypos., n = 7), predominantly presenting as mast cell leukemia (MCL; 6/7 patients), (b) MCL with negative KIT sequencing (KITneg. MCL, n = 7) and (c) KITneg. SM with associated hematologic neoplasm (KITneg. SM-AHN, n = 5). Although >70% of patients in the two MCL cohorts (KIT D816H/Ypos. and KITneg.) were classified as low/intermediate risk according to prognostic scoring systems (PSS), treatment response was poor and median OS was shorter than in a KIT D816Vpos. MCL control cohort (n = 29; 1.7 vs. 0.9 vs. 2.6 years; p < 0.04). The KITneg. SM-AHN phenotype was dominated by the heterogeneous AHN (low mast cell burden, presence of additional mutations) with a better median OS of 4.5 years. We conclude that (i) in MCL, negativity for D816V is a relevant prognostic factor and (ii) PSS fail to correctly classify D816Vneg. patients.

[Mastocytosis in children]

Mastocytosis in children is a rare disease characterized by an abnormal accumulation of tissue mast cells. Mastocytosis in children presents with typical skin alterations that are classified as maculopapular cutaneous mastocytosis, diffuse cutaneous mastocytosis, or mastocytoma. Some patients also develop mast cell mediator symptoms, such as pruritus, flush, and anaphylaxis. In many children, the disease is characterized by a benign and usually self-limiting course; systemic mastocytosis with extracutaneous involvement and a chronic or progressive course is found only rarely. Therapeutically, H1 antihistamines are primarily used on an as-needed basis or as continuous treatment, depending on the severity. Children, parents and caregivers should be thoroughly educated about the clinical picture and possible trigger factors of mast cell mediator release. For children with extensive skin alterations and severe symptoms, the prescription of an epinephrine auto-injector is recommended for emergency treatment.

Comprehensive Analysis of Acquired Genetic Variants and Their Prognostic Impact in Systemic Mastocytosis

Systemic mastocytosis (SM) is a rare clonal haematopoietic stem cell disease in which activating KIT mutations (most commonly KIT D816V) are present in virtually every (>90%) adult patient at similar frequencies among non-advanced and advanced forms of SM. The KIT D816V mutation is considered the most common pathogenic driver of SM. Acquisition of this mutation early during haematopoiesis may cause multilineage involvement of haematopoiesis by KIT D816V, which has been associated with higher tumour burden and additional mutations in other genes, leading to an increased rate of transformation to advanced SM. Thus, among other mutations, alterations in around 30 genes that are also frequently mutated in other myeloid neoplasms have been reported in SM cases. From these genes, 12 (i.e., ASXL1, CBL, DNMT3A, EZH2, JAK2, KRAS, NRAS, SF3B1, RUNX1, SF3B1, SRSF2, TET2) have been recurrently reported to be mutated in SM. Because of all the above, assessment of multilineage involvement of haematopoiesis by the KIT D816V mutation, in the setting of multi-mutated haematopoiesis as revealed by a limited panel of genes (i.e., ASXL1, CBL, DNMT3A, EZH2, NRAS, RUNX1 and SRSF2) and associated with a poorer patient outcome, has become of great help to identify SM patients at higher risk of disease progression and/or poor survival who could benefit from closer follow-up and eventually also early cytoreductive treatment.

Cutaneous and splenic mastocytosis in a juvenile Malayan tiger

A male Malayan tiger cub developed well-circumscribed, erythematous, alopecic lesions on the face, torso, and paws when 1-wk-old. Biopsies of a torso lesion and a right front paw lesion at 1-mo-old confirmed cutaneous mast cell tumors (MCTs). MCTs on the paws grew into pendulous masses up to 6.5 cm in diameter by 3-mo-old, but those on the face and torso regressed. Fine-needle aspiration of the spleen at 3-mo-old revealed marked mast cell infiltration. The spleen and the right paw cutaneous MCT were removed; the paw MCT recurred within 7 d. A 12-bp tandem duplication, suggesting a somatic mutation, was identified in exon 8 of c-KIT in DNA extracted from the cutaneous MCT on the right paw and from one over the torso, but not from the spleen. Remaining MCTs on the paws regressed slowly following splenectomy and had completely regressed by 1-y-old. At 7-y-old, there was no recurrence of any mast cell disease. Mast cell disease in this tiger cub is similar to a report in a domestic kitten and to pediatric mastocytosis in humans, which commonly begins in infancy, improves by adolescence, and is associated with somatic c-kit mutations. To our knowledge, mastocytosis has not been reported previously in a juvenile exotic felid.

Clinicopathological Profile of Childhood Onset Cutaneous Mastocytosis from a Tertiary Care Center in South India

Background

Mastocytosis is characterized by clonal proliferation of mast cells in various organs and can have isolated cutaneous or systemic involvement. Childhood-onset mastocytosis (COM) is usually cutaneous and regresses spontaneously, while adult-onset mastocytosis (AOM) is often persistent with systemic involvement. There is limited data on COM from India.

Objective

To elucidate the clinicopathological profile of COM.

Methods

We conducted a retrospective chart review of all the patients with histologically proven COM (≤16 years), presenting over 11 years (January 2009 to December 2019) to the Dermatology Department. We compiled the demographic data, clinical characteristics (morphology, extent, distribution), laboratory investigations, histopathology findings, imaging (ultrasound abdomen), c-KIT mutation results, where available, and other associated abnormalities, and grouped them according to the WHO classification for mastocytosis.

Results

Among the 66 patients with COM (M: F-1.6:1), 89.4% had onset before 2 years of age. The subtypes were: maculopapular cutaneous mastocytosis (MPCM: 44, 66.7%); mastocytoma of the skin (MOS: 19, 28.8%); diffuse cutaneous mastocytosis (DCM: 2, 3%) and indolent systemic mastocytosis (ISM: 1, 1.5%). Blistering was observed in 29 (43.9%) and Darier sign was elicited in 47 (71.2%) patients. Serum tryptase was elevated in 9/21 (42.9%) patients, but none had systemic mastocytosis. Three patients had c-KIT mutations (two in exon 8 and one in exon 17). Most patients were managed symptomatically and the patient with ISM improved with imatinib.

Conclusion

MPCM is the most common variant of COM and most patients had a disease onset before 2 years. Overall, COM had a good prognosis with rare systemic involvement, mitigating the need for extensive evaluation routinely in children.

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.

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

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

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.

Clinical Impact of Skin Lesions in Mastocytosis: A Multicenter Study of the European Competence Network on Mastocytosis

Mastocytosis is a rare neoplasm characterized by the expansion and accumulation of mast cells in various organ systems. Systemic mastocytosis (SM) may or may not present with cutaneous lesions. To examine the frequency and clinical impact of cutaneous involvement, data on 1,510 patients with mastocytosis collected in the registry of the European Competence Network on Mastocytosis were analyzed. Cutaneous involvement was found in 1,195 of 1,510 patients (79.1%). Of these, 286 had cutaneous mastocytosis, and 721 had SM with skin involvement. Adult patients with skin involvement who did not have a bone marrow examination (n = 188) were defined as having mastocytosis in the skin. In 315 patients, SM without skin involvement was found. The percentage of cases with cutaneous involvement was higher in indolent SM (100%) and smoldering SM (87.9%) compared to aggressive SM (46.8%) or mast cell leukemia (38.5%). After a median follow-up of 5.6 years, no patient with cutaneous mastocytosis had died, but 2.6% of the patients with mastocytosis in the skin, 5.7% of the patients with SM with skin involvement, and 28.95% of the patients with SM without skin involvement had died. Overall survival was longer in patients with skin involvement (cutaneous mastocytosis and/or mastocytosis in the skin and/or SM with skin involvement) than in patients with SM without skin involvement (P < 0.0001). These data argue for a thorough examination of both the skin and bone marrow in adult patients with mastocytosis.

Criteria for the Regression of Pediatric Mastocytosis: A Long-Term Follow-Up

BACKGROUND

Mastocytosis is a neoplastic condition characterized by the accumulation of mast cells (MCs) in 1 or more organ. Adults tend to have persistent, systemic mastocytosis, whereas MC infiltration in children is usually limited to the skin and typically regresses after several years. Both adults and children could display mast cell activation symptoms (MCASs) due to MC mediator release. In more than 85% of both adult and pediatric cases, KIT mutations are present, with the KIT D816V mutation being present in most affected adults but in only half the affected children.

OBJECTIVE

To identify the clinical, biological, and molecular factors associated with the regression of cutaneous mastocytosis (CM) in children, and to assess the correlation between MCASs and CM regression.

METHODS

Patients having suffered from pediatric-onset mastocytosis for at least 8 years were included in a longitudinal cohort study. Clinical data, the baseline serum tryptase level, the KIT sequence, and the progression of MCASs and CM were recorded.

RESULTS

CM regressed in 210 of the 272 included patients (77.2%; mean time to regression, 6.10 years). The rare cases of aggressive systemic mastocytosis were symptomatic from the outset. Congenital mastocytosis and the KIT D816V mutation were associated with CM regression (odds ratio, 0.48, P = .031, and 0.173, P = .031, respectively). Aggravation of MCASs over time was correlated with the persistence of skin lesions. However, the MCASs became more intense in 19% of the patients with MCASs at baseline and CM regression, justifying long-term follow-up in this setting.

CONCLUSIONS

Our results open up new hypotheses with regard to the spontaneous regression of CM in pediatric patients.

Genotypic and phenotypic characteristics of Chinese neonates with cutaneous mastocytosis: a case report and literature review

Mastocytosis is an accumulation of clonal mast cells within tissues and it is most commonly caused by an activating mutation in the KIT gene. In this study, we report a neonatal case who presented with diffuse cutaneous mastocytosis (CM) at birth. In China, nine other cases of neonatal-onset CM have been reported in the literature since 2006. In those cases, diffuse CM and urticaria pigmentosa were the main symptoms, and mutations in exon 17 at codon 816 in KIT were identified.

Detection of the KITD816V mutation in myelodysplastic and/or myeloproliferative neoplasms and acute myeloid leukemia with myelodysplasia-related changes predicts concurrent systemic mastocytosis

Greater than 90% of cases of systemic mastocytosis (SM) harbor pathogenic KIT mutations, particularly KIT^D816V. Prognostically-significant pathogenic KIT mutations also occur in 30-40% of core binding factor-associated acute myeloid leukemia (CBF-AML), but are uncommonly associated with concurrent SM. By comparison, the occurrence of SM in other myeloid neoplasms bearing pathogenic KIT mutations, particularly those with a chronic course, is poorly understood. Review of clinical next-generation sequencing (NGS) performed at our institutions in patients with known or suspected hematologic malignancies over an 8-year period revealed 64 patients with both a pathogenic KIT mutation detected at one or more timepoints and available bone marrow biopsy materials. Patients with KIT^D816V-mutated myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), or overlap MDS/MPN (n = 22) accounted for approximately one-third of our cohort (34%). Comprehensive morphologic and immunophenotypic characterization revealed that nearly all cases (n = 20, 91%) exhibited concurrent SM. In contrast, of the 18 patients (28%) with AML and KIT^D816V, only eight (44%) showed evidence of SM at any point in their disease course (p = 0.0021); of these eight, the AML component was characterized as AML with myelodysplasia-related changes (AML-MRC) in all but one instance (n = 7, 87%). Twelve patients (19%) had pathogenic KIT mutations other than p.D816V, all in the setting of AML (CFB-AML, n = 7; AML, not otherwise specified, n = 2; AML-MRC, n = 1; acute promyelocytic leukemia, n = 1); only two of these patients (17%), both with CBF-AML, exhibited concurrent SM. The remaining 12 patients (19%) had SM without evidence of an associated hematological neoplasm (AHN). For nearly one-third of the 30 SM-AHN patients in our cohort (n = 9, 30%), the SM component of their disease was not initially clinicopathologically recognized. We propose that identification of the KIT^D816V mutation in patients diagnosed with MDS, MPN, MDS/MPN, or AML-MRC should trigger reflex testing for SM.

Frequency of isolated cutaneous involvement in adult mastocytosis: a cohort study

BACKGROUND

Mastocytosis is characterized by the accumulation/proliferation of abnormal mast cells. The frequency of isolated cutaneous involvement in adults with mastocytosis has not been fully determined. The main objective of our study was to assess the frequency of isolated cutaneous mastocytosis (CM) in adults with mastocytosis skin lesions. The second objective was to compare the clinical, histological, biological and imaging features in patients with isolated CM and patients with systemic mastocytosis (SM).

METHODS

We included all patients with histology-proven mastocytosis skin lesions between January 2009 and December 2017. The mastocytosis diagnosis was made according to the international diagnostic criteria. All data were collected from a dedicated specific case report.

RESULTS

Among 160 patients with mastocytosis skin lesions, 25 patients had isolated CM (15.6%), 105 had SM and 30 (18.7%) patients had undetermined mastocytosis. Skin KIT mutation (OR: 51.9, 95% CI: 3.9-678, P = 0.001) and high bone marrow tryptase (OR: 97.4, 95% CI: 10.3-915, P = 0.001) were strong predictors of SM. The prevalence of osteoporosis was higher in the SM population than in the isolated CM population. Moreover, a decrease in bone mineral density over a short period of follow-up (1-2 years) was associated with SM. There were no differences between the two groups regarding the frequency of mast cell activation symptoms, the presentation of skin lesions, the number of mast cells in the dermis and the level of serum tryptase. We propose considering the KIT mutation status and bone marrow tryptase levels to aid the diagnosis of isolated CM in adult mastocytosis patients.

CONCLUSION

Only a small minority of adults with mastocytosis skin lesions has isolated cutaneous involvement. In 18.7% of mastocytosis cases, even complete workup does not allow for a precise classification of patients.

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.

Prevalence and risk factors for fragility fracture in systemic mastocytosis

OBJECTIVES

Systemic mastocytosis (SM) is characterized by the accumulation of mast cells in tissues other than the skin. Bone involvement although frequent has not been thoroughly evaluated. Primary objective was to determine risk factors associated with fragility fractures (FF) in SM. Secondary objectives were to evaluate the ability of bone marrow tryptase (BMT) level to identify patients with FF, and to describe bone involvement in SM.

METHODS

We analyzed retrospectively all consecutive patients seen in our expert center, with a diagnosis of SM according to the 2001 WHO criteria, and with complete bone assessment. We collected data about lifetime fractures, types of cutaneous manifestations, degranulation symptoms, blood and BMT levels, bone mineral density assessed by densitometry and KIT mutation. We performed a univariate analysis investigating the factors associated with FF and then a logistic multivariable regression analysis. We assessed the ability of bone marrow tryptase to identify patients with FF.

RESULTS

Eighty-nine patients with SM were included. Thirty-six patients (40.4%) suffered from osteoporosis and twenty-five (28.1%) experienced lifetime FF. Univariate analysis identified age at diagnosis and disease onset, presence of telangiectasia macularis eruptiva perstans, digestive symptoms, mast cells activation symptoms, elevated BMT, low femoral and lumbar BMD, as associated with FF. Multivariate analysis identified elevated BMT, low femoral T score and older age at diagnosis as independently associated with FF.

CONCLUSIONS

Low femoral T-score, BMT level, and older age at diagnosis are markers associated with FF in SM. BMT may represent an important biomarker to predict FF in SM patients.

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.

In utero presentation of aggressive systemic mastocytosis in a neonate

Mastocytosis is a clinically heterogenous disease characterized by mast cell hyperplasia in skin, bone marrow and/or visceral organs. Cutaneous mastocytosis is more frequently observed in children, whereas indolent systemic mastocytosis is more commonly observed in adults. Aggressive systemic presentation, particularly of the neonate, is exceptionally rare. We present a rare case of congenital aggressive systemic mastocytosis. The patient was a 37-week-old male, born by caesarean section owing to hepatosplenomegaly and ascites diagnosed in utero, who exhibited extensive cutaneous and systemic manifestations of mastocytosis at birth. Mutation analysis of c-KIT identified D816V mutation in exon 17. Although initial bilateral bone marrow aspirates demonstrated no mast-cell infiltrates or haematological neoplasm, subsequent bone-marrow biopsies postmortem exhibited multifocal mast-cell aggregates. Clinical course was complicated by bacteraemia and cardiorespiratory failure, leading to death at 10 weeks.

Targeted Treatment Options in Mastocytosis

Mastocytosis refers to a heterogeneous group of disorders resulting from the clonal proliferation of abnormal mast cells and their accumulation in the skin (cutaneous mastocytosis when only in the skin, CM) or in various organs (systemic mastocytosis, SM). This leads to a wide variety of clinical manifestations resulting from excessive mediator release in CM and benign forms of SM (indolent SM, ISM) and from tissue mast cell infiltration causing multiorgan dysfunction and failure in more aggressive subtypes (aggressive SM, ASM, or mast cell leukemia). In addition, SM may be associated with hematological neoplasms (AHN). While treatment of ISM primarily aims at symptom management with anti-mediator therapies, cytoreductive and targeted therapies are needed to control the expansion of neoplastic mast cells in advanced forms of SM, in order to improve overall survival. Mast cell accumulation results from a gain-of-function mutation (mostly the D816V mutation) within the KIT tyrosine kinase domain expressed by mast cells and additional genetic and epigenetic mutations may further determine the features of the disease (ASM and AHN). Consequently, tyrosine kinase inhibitors and targeted therapies directed against the oncogenic signaling machinery downstream of KIT are attractive therapeutic approaches. A better understanding of the relative contribution of these genetic and epigenetic events to the molecular pathogenesis of mastocytosis is of particular interest for the development of targeted therapies and therefore to better choose patient subgroups that would best benefit from a given therapeutic strategy.

Systemic mastocytosis with KIT V560G mutation presenting as recurrent episodes of vascular collapse: response to disodium cromoglycate and disease outcome

Background

Mastocytosis are rare diseases characterized by an accumulation of clonal mast cells (MCs) in one or multiple organs or tissues. Patients with systemic mastocytosis (SM), whose MCs frequently arbor the activating D816V KIT mutation, may have indolent to aggressive diseases, and they may experience MC mediator related symptoms. Indolent SM with recurrent anaphylaxis or vascular collapse in the absence of skin lesions, ISMs(−), is a specific subtype indolent SM (ISM), and this clonal MC activation disorder represents a significant fraction of all MC activation syndromes. The V560G KIT mutation is extremely rare in patients with SM and its biological and prognostic impact remains unknown.

Case presentation

A 15-year old boy was referred to our hospital because of repeated episodes of flushing, hypotension and syncope since the age of 3-years, preceded by skin lesions compatible with mastocytosis on histopathology that had disappeared in the late-early childhood. Diagnosis of ISM, more precisely the ISMs(−) variant, was confirmed based on the clinical manifestations together with increased baseline serum tryptase levels and the presence of morphologically atypical, mature appearing (CD117+high, FcεRI+) phenotypically aberrant (CD2+, CD25+) MCs, expressing activation-associated markers (CD63, CD69), in the bone marrow. Molecular genetic studies revealed the presence of the KIT V560G mutation in bone marrow MCs, but not in other bone marrow cells, whereas the screening for mutations in codon 816 of KIT was negative. The patient was treated with oral disodium cromoglycate and the disease had a favorable outcome after an eleven-year follow-up period, during which progressively lower serum tryptase levels together with the fully disappearance of all clinical manifestations was observed.

Conclusions

To the best of our knowledge this first report of a patient with ISM, whose bone marrow MCs carry the KIT V560G activating mutation, manifesting as recurrent spontaneous episodes of flushing and vascular collapse in the absence of skin lesions at the time of diagnosis, in whom disodium cromoglycate had led to long term clinical remission.

Clinical features of mastocytosis at pediatric patients

Mastocytosis is relevant to heterogeneous disease group characterized with redundant accumulation and proliferation of mast cells in tissues. The skin form of mastocytosis is mainly occurs in children. The article contains the current data on etiology, pathogenesis, classification, clinical forms, diagnosis, prophylactics and mastocytosis treatment at children.

Transgenerational transmission of systemic mast cell activation disease-genetic and epigenetic features

Systemic mast cell activation disease (MCAD) comprises disorders characterized by an enhanced release of mast cell mediators accompanied by a varying accumulation of dysfunctional mast cells. Within the last years, evidence has been presented that MCAD is a multifactorial polygenic determined disease with the KIT(D816V) mutation and its induced functional consequences considered as special case. The respective genes encode proteins for various signaling pathways, epigenetic regulators, the RNA splicing machinery, and transcription factors. Transgenerational transmission of MCAD appears to be quite common. The basics of the molecular mechanisms underlying predisposition of the disease, that is, somatic and germline mutations and the contribution of epigenetic processes have become identifiable. The aim of the present review is to present and discuss available genetic, epigenetic and epidemiological findings, and to present a model of MCAD pathogenesis.

Receptor tyrosine kinase (c-Kit) inhibitors: a potential therapeutic target in cancer cells

c-Kit, a receptor tyrosine kinase, is involved in intracellular signaling, and the mutated form of c-Kit plays a crucial role in occurrence of some cancers. The function of c-Kit has led to the concept that inhibiting c-Kit kinase activity can be a target for cancer therapy. The promising results of inhibition of c-Kit for treatment of cancers have been observed in some cancers such as gastrointestinal stromal tumor, acute myeloid leukemia, melanoma, and other tumors, and these results have encouraged attempts toward improvement of using c-Kit as a capable target for cancer therapy. This paper presents the findings of previous studies regarding c-Kit as a receptor tyrosine kinase and an oncogene, as well as its gene targets and signaling pathways in normal and cancer cells. The c-Kit gene location, protein structure, and the role of c-Kit in normal cell have been discussed. Comprehending the molecular mechanism underlying c-Kit-mediated tumorogenesis is consequently essential and may lead to the identification of future novel drug targets. The potential mechanisms by which c-Kit induces cellular transformation have been described. This study aims to elucidate the function of c-Kit for future cancer therapy. In addition, it has c-Kit inhibitor drug properties and their functions have been listed in tables and demonstrated in schematic pictures. This review also has collected previous studies that targeted c-Kit as a novel strategy for cancer therapy. This paper further emphasizes the advantages of this approach, as well as the limitations that must be addressed in the future. Finally, although c-Kit is an attractive target for cancer therapy, based on the outcomes of treatment of patients with c-Kit inhibitors, it is unlikely that Kit inhibitors alone can lead to cure. It seems that c-Kit mutations alone are not sufficient for tumorogenesis, but do play a crucial role in cancer occurrence.

Mastocytosis among elderly patients: A multicenter retrospective French study on 53 patients

Mastocytosis is a heterogeneous group of diseases with a young median age at diagnosis. Usually indolent and self-limited in childhood, the disease can exhibit aggressive progression in mid-adulthood. Our objectives were to describe the characteristics of the disease when diagnosed among elderly patients, for which rare data are available.The French Reference Center conducted a retrospective multicenter study on 53 patients with mastocytosis >69 years of age, to describe their clinical, biological, and genetic features.The median age of our cohort of patients was 75 years. Mastocytosis variants included were cutaneous (n = 1), indolent systemic (n = 5), aggressive systemic (n = 11), associated with a hematological non-mast cell disease (n = 34), and mast cell leukemia (n = 2). Clinical manifestations were predominantly mast cell activation symptoms (75.5%), poor performance status (50.9%), hepatosplenomegaly (50.9%), skin involvement (49.1%), osteoporosis (47.2%), and portal hypertension and ascites (26.4%). The main biological features were anemia (79.2%), thrombocytopenia (50.9%), leucopenia (20.8%), and liver enzyme abnormalities (32.1%). Of the 40 patients tested, 34 (85%), 2 (5%), and 4 (10%) exhibited the KIT D816V mutant, other KIT mutations and the wild-type form of the KIT gene, respectively. Additional sequencing detected significant genetic defects in 17 of 26 (65.3%) of the patients with associated hematological non-mast cell disease, including TET2, SRSF2, IDH2, and ASLX1 mutations. Death occurred in 19 (35.8%) patients, within a median delay of 9 months, despite the different treatment options available.Mastocytosis among elderly patients has a challenging early detection, rare skin involvement, and/or limited skin disease; it is heterogeneous and has often an aggressive presentation with nonfortuitous associated myeloid lineage malignant clones, and thus a poor overall prognosis.

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.

Novel R634W c-kit mutation identified in familial mastocytosis

Familial mastocytosis is a well-documented but rare entity, with fewer than 100 cases reported in the literature. The etiology has most commonly been linked to activating c-kit mutations, with several mutations reported to date. We present a novel familial mastocytosis-associated c-kit mutation (R634W) in three siblings with urticaria pigmentosa. This mutation has been previously described in mucosal melanoma, chronic myelomonocytic leukemia, and acute myeloid leukemia. Because this is a rare mutation, it is unclear whether screening for other disease states associated with the mutation would be of benefit.

Evidence for contribution of epigenetic mechanisms in the pathogenesis of systemic mast cell activation disease

Recently, evidence was provided for common familial occurrence of systemic mast cell activation disease (MCAD), i.e., mast cell disorders characterized by aberrant release of mast cell mediators and/or accumulation of pathological mast cells in potentially any tissue. Since there is accumulating evidence that epigenetic processes may have transgenerational consequences, the aim of the present study was to investigate by two different experimental approaches whether epigenetic effects may contribute to the familial occurrence of MCAD. (1) High throughput profiling of the methylation status of the genomic DNA in leukocytes from MCAD patients in comparison to healthy subjects revealed for the first time an association of MCAD with alterations in DNA methylation comprising genes encoding proteins crucially involved in DNA/RNA repair and processing, apoptosis, cell activity, and exocytosis/cell communication. A set of 195 differentially methylated CpG sites could be regarded as candidates for a MCAD signature at the methylation level of the DNA. (2) In a cohort of MCAD patients, a correlation between age at symptom onset and year of birth (reflecting different generations) was observed suggesting the presence of the phenomenon of anticipation. In conclusion, the present findings suggest that epigenetic processes could substantially contribute to the transgenerational transmission of MCAD.

ASXL1 but not TET2 mutations adversely impact overall survival of patients suffering systemic mastocytosis with associated clonal hematologic non-mast-cell diseases

Systemic mastocytosis with associated hematologic clonal non-mast cell disease (SM-AHNMD) is a rare and heterogeneous subtype of SM and few studies on this specific entity have been reported. Sixty two patients with Systemic mastocytosis with associated hematologic clonal non-mast cell disease (SM-AHNMD) were presented. Myeloid AHNMD was the most frequent (82%) cases. This subset of patients were older, had more cutaneous lesions, splenomegaly, liver enlargement, ascites; lower bone mineral density and hemoglobin levels and higher tryptase level than lymphoid AHNMD. Defects in KIT, TET2, ASXL1 and CBL were positive in 87%, 27%, 14%, and 11% of cases respectively. The overall survival of patients with SM-AHNMD was 85.2 months. Within the myeloid group, SM-MPN fared better than SM-MDS or SM-AML (p = 0.044,). In univariate analysis, the presence of C-findings, the AHNMD subtypes (SM-MDS/CMML/AML versus SM-MPN/hypereosinophilia) (p = 0.044), Neutropenia (p = 0.015), high monocyte level (p = 0.015) and the presence of ASXL1 mutation had detrimental effects on OS (p = 0.007). In multivariate analysis and penalized Cox model, only the presence of ASXL1 mutation remained an independent prognostic factor that negatively affected OS (p = 0.035). SM-AHNMD is heterogeneous with variable prognosis according to the type of the AHNMD. ASXL1 is mutated in a subset of myeloid AHNMD and adversely impact on OS.

Adult-onset mastocytosis in the skin is highly suggestive of systemic mastocytosis

Adult-onset urticaria pigmentosa/mastocytosis in the skin almost always persists throughout life. The prevalence of systemic mastocytosis in such patients is not precisely known. Bone marrow biopsies from 59 patients with mastocytosis in the skin and all available skin biopsies (n=27) were subjected to a meticulous cytological, histological, immunohistochemical, and molecular analysis for the presence of WHO-defined diagnostic criteria for systemic mastocytosis: compact mast cell infiltrates (major criterion); atypical mast cell morphology, KIT D816V, abnormal expression of CD25 by mast cells, and serum tryptase levels >20 ng/ml (minor criteria). Systemic mastocytosis is diagnosed when the major diagnostic criterion plus one minor criterion or at least three minor criteria are fulfilled. Systemic mastocytosis was confirmed in 57 patients (97%) by the diagnosis of compact mast cell infiltrates plus at least one minor diagnostic criterion (n=42, 71%) or at least three minor diagnostic criteria (n=15, 25%). In two patients, only two minor diagnostic criteria were detectable, insufficient for the diagnosis of systemic mastocytosis. By the use of highly sensitive molecular methods, including the analysis of microdissected mast cells, KIT D816V was found in all 58 bone marrow biopsies investigated for it but only in 74% (20/27) of the skin biopsies. It is important to state that even in cases with insufficient diagnostic criteria for systemic mastocytosis, KIT D816V-positive mast cells were detected in the bone marrow. This study demonstrates, for the first time, that almost all patients with adult-onset mastocytosis in the skin, in fact, have systemic mastocytosis with cutaneous involvement.

Distinct signalling pathways for mutated KIT(V560G) and KIT(D816V) in mastocytosis

BACKGROUND

The activating mutations KIT(V560G) and KIT(D816V) are associated with mastocytosis. Thus, identifying and inhibiting the signalling pathways associated with mutated KIT gene offers a potentially important strategy for the treatment of mastocytosis.

AIM

To correlate KIT mutations with specific signalling pathways in human mast-cell lines using pathway inhibitors.

METHODS

Human mast-cell (HMC) lines expressing KIT(V560G) (the cell line HMC-1) and KIT(V560G and D816V) (HMC-1.2) were treated with specific signalling pathway inhibitors for 1-5 days, and the inhibitory effects on growth were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell-proliferation assay, western blotting and flow cytometry.

RESULTS

Growth inhibitory assays and western blot analyses showed that the Janus kinase 3/signal transducer and activator of transcription (JAK3/STAT) pathway is the preferential signalling pathway for KIT(V560G), whereas the mechanistic target of rapamycin complex 1/4E-binding protein 1 (mTORC1/4E-BP1) pathway is preferentially linked to KIT(D816V). Inhibition of these critical signalling pathways results in programmed cell death.

CONCLUSIONS

KIT(V560G) and KIT(D816V) use different signalling pathways that promote mast-cell growth. Inhibitors of these specific pathways might be effective in treating mastocytosis.

Identification of KIT activating mutations in paediatric solitary mastocytoma

AIMS

Mastocytosis is an abnormal mast cell proliferation involving one or more organs, in particular the skin and bone marrow. In children, disease is usually limited to the skin, with three distinct clinical presentations: urticaria pigmentosa, diffuse cutaneous mastocytosis and solitary mastocytoma. Although the KIT D816V mutation is typically found in adult-onset mastocytosis, it is less commonly seen in childhood-onset mastocytosis, and the frequency of KIT mutations in paediatric solitary mastocytoma is poorly documented.

METHODS AND RESULTS

In this study we analysed KIT exons 8, 9, 11, 13 and 17 in nine cases of paediatric solitary mastocytoma using a laboratory-developed Sanger sequencing assay. A KIT mutation was identified in six cases (67%), including three with the D816V mutation typical of adult-onset disease, and another three with an internal tandem duplication (p.A502_Y503dup) in exon 9, previously described in gastrointestinal stromal tumour.

CONCLUSIONS

Paediatric solitary mastocytoma is frequently associated with KIT activating mutations, in keeping with a clonal process. KIT mutational status appears insufficient to explain the divergent biology of childhood and adult-onset disease.

Mastocytosis

Mastocytosis is a disorder of abnormal mast cell proliferation, with clinical features that include flushing, pruritus, abdominal pain, diarrhea, hypotension, syncope, and musculoskeletal pain. These features are the result of mast cell mediator release and infiltration into target organs. Patients of all ages may be affected, although in children, manifestations primarily involve the skin. Most patients with systemic disease have a somatically acquired activating mutation in the KIT oncogene. This article discusses the causes and pathogenesis of mastocytosis, with an overview of the clinical features and the approach to diagnosis, evaluation, and therapy in adults and pediatric patients.

Gastrointestinal manifestations in mastocytosis: a study of 83 patients

BACKGROUND

Mastocytosis is a heterogeneous disease characterized by mast cell accumulation in 1 or more organs. Gastrointestinal manifestations of systemic mastocytosis have been previously studied in small cohorts of patients, and no specific histologic description is available.

OBJECTIVE

We sought to assess the clinical and pathologic features of gastrointestinal manifestations in patients with mastocytosis.

METHODS

Medical history and gastrointestinal symptoms of patients with mastocytosis (n = 83) were compared with those of matched healthy subjects (n = 83) by means of patient questionnaire. Data were analyzed for epidemiologic, clinical, biological, and genetic factors associated with gastrointestinal symptoms for patients with mastocytosis. A comparative analysis of gastrointestinal histology from patients with mastocytosis (n = 23), control subjects with inflammatory bowel disease (n = 17), and healthy subjects (n = 19) was performed.

RESULTS

The following gastrointestinal symptoms occurred more frequently and were more severe in patients with mastocytosis than in healthy subjects: bloating (33% vs 7.2%, P < .0001), abdominal pain (27.3% vs 4.8%, P < .0001), nausea (23% vs 8.4%, P = .02), and diarrhea (33.85% vs 1.2%, P < .0001). Patients with mastocytosis had a significantly higher incidence of personal history of duodenal ulcer (P = .02). Wild-type (WT) c-Kit was associated with diarrhea (P = .03). Specific histologic lesions were present in patients with mastocytosis but were not correlated with clinical symptoms.

CONCLUSION

Gastrointestinal manifestations in patients with mastocytosis are highly prevalent and often severe. Clinical symptoms do not correspond to histologic findings, are nonspecific, and can simulate irritable bowel syndrome.

A subset of gastrointestinal stromal tumors previously regarded as wild-type tumors carries somatic activating mutations in KIT exon 8 (p.D419del)

About 10-15% of gastrointestinal stromal tumors (GISTs) carry wild-type sequences in all hot spots of KIT and platelet-derived growth factor receptor alpha (PDGFRA) (wt-GISTs). These tumors are currently defined by having no mutations in exons 9, 11, 13, and 17 of the KIT gene and exons 12, 14, and 18 of the PDGFRA gene. Until now, the analysis of further exons is not recommended. However, we have previously published a report on a KIT exon 8 germline mutation, which was associated with familial GIST and mastocytosis. We therefore investigated whether KIT exon 8 mutations might also occur in sporadic GIST. We screened a cohort of 145 wt-GISTs from a total of 1351 cases from our registry for somatic mutations in KIT exon 8. Two primary GISTs with an identical exon 8 mutation (p.D419del) were detected, representing 1.4% of all the cases analyzed. Based on all GISTs from our registry, the overall frequency of KIT exon 8 mutations was 0.15%. The first tumor originating in the small bowel of a 53-year-old male patient had mostly a biphasic spindled-epithelioid pattern with a high proliferative activity (14 mitoses/50 HPF) combined with a second low proliferative spindle cell pattern (4/50 HPF). The patient developed multiple peritoneal metastases 29 months later. The second case represented a jejunal GIST in a 67-year old woman who is relapse-free under adjuvant imatinib treatment. We conclude that about 1-2% of GISTs being classified as 'wild type' so far might, in fact, carry KIT mutations in exon 8. Moreover, this mutational subtype was shown to be activating and imatinib sensitive in vitro. We therefore propose that screening for KIT exon 8 mutations should become a routine in the diagnostic work-up of GIST and that patients with an exon 8 mutation and a significant risk for tumor progression should be treated with imatinib.