Standards and standardization in mastocytosis: consensus statements on diagnostics, treatment recommendations and response criteria

Eosinophilic myeloproliferative disorders

Despite recent attempts to define and classify patients with marked eosinophilia and features consistent with myeloproliferative disease, areas of controversy remain. These are particularly apparent in situations in which multiple lineages are involved in a clonal process and clinical manifestations are overlapping. Although the introduction of new molecular diagnostics and targeted therapies has begun to clarify the boundaries between some of these disorders, several questions remain with respect to the classification of patients with myeloproliferative hypereosinophilic syndrome (HES) of unknown etiology.

Omalizumab treatment of systemic mast cell activation disease: experiences from four cases

We report on the outcome of 4 patients with therapy-resistant systemic mast cell activation disease (MCAD) treated with the anti-IgE monoclonal antibody omalizumab in compassionate use. Two patients achieved an impressive persistent clinical response to treatment with omalizumab. In the third patient symptoms gradually improved. In the fourth patient omalizumab treatment had to be discontinued due to intolerable mast cell mediator-induced symptoms. In conclusion, omalizumab can lessen the intensity of the symptoms of systemic MCAD. Hence, omalizumab should be considered as a therapeutic option in cases of systemic MCAD that are resistant to evidence-based therapy.

Hypotension, Syncope, and Fever in Systemic Mastocytosis without Skin Infiltration and Rapid Response to Corticosteroid and Cyclosporin: A Case Report

Mast cell disorders are defined by an abnormal accumulation of tissue mast cells in one or more organ systems. In systemic mastocytosis, at least one extracutaneous organ is involved by definition. Although, systemic mastocytosis usually represents with skin lesion called urticaria pigmentosa, in a small proportion, there is extracutaneous involvement without skin infiltration. Other manifestations are flushing, tachycardia, dyspepsia, diarrhea, hypotension, syncope, and rarely fever. Various medications have been used but there is not a definite cure for systemic mastocytosis. The principles of treatment include control of symptoms with measures aimed to decrease mast cell activation. We describe a case of systemic mastocytosis presenting with hypotension, syncope attacks, fever, and local flushing. In bone marrow biopsy, increased mast cell infiltration was demonstrated. She had no skin infiltration. A good clinicopathological response was obtained acutely with combination therapy of glucocorticoid and cyclosporine.

Mast cell activation syndrome: Proposed diagnostic criteria

The term mast cell activation syndrome (MCAS) is finding increasing use as a diagnosis for subjects who present with signs and symptoms involving the dermis, gastrointestinal track, and cardiovascular system frequently accompanied by neurologic complaints. Such patients often have undergone multiple extensive medical evaluations by different physicians in varied disciplines without a definitive medical diagnosis until the diagnosis of MCAS is applied. However, MCAS as a distinct clinical entity has not been generally accepted, nor do there exist definitive criteria for diagnosis. Based on current understanding of this disease "syndrome" and on what we do know about mast cell activation and resulting pathology, we will explore and propose criteria for its diagnosis. The proposed criteria will be discussed in the context of other disorders involving mast cells or with similar presentations and as a basis for further scientific study and validation.

Evaluation of basophil activation in mastocytosis with Hymenoptera venom anaphylaxis

BACKGROUND

Basophil activation tests (BATs) have been demonstrated to be useful in detecting IgE-mediated sensitization by measuring basophil activation surface markers (CD63 and CD203c). Hymenoptera venom is one of the best known mediators-release trigger in patients with systemic mastocytosis (SM). The aim of this study was to investigate the use of BATs as an additional diagnostic tool in patients with mastocytosis suffering from hymenoptera venom anaphylaxis (HVA).

METHODS

A total of 22 patients with history of HVA and SM, together with a group of 11 patients with HVA in whom SM was ruled out after a complete bone marrow study, were analyzed.

RESULTS

Among 11 SM patients who had specific serum IgE (sIgE) against hymenoptera venom and an evaluable BAT, a positive BAT was found in nine. Additionally, a positive BAT was detected in three of seven patients who had no sIgE. These three patients had low levels of total IgE compared with control population (mean of 20 vs. 78 IU/mL); one had discontinued immunotherapy after 5 years, when sIgE levels had turned negative, and, in the other two patients, BAT identified the culprit insect.

CONCLUSIONS

BAT is a useful complementary diagnostic tool to sIgE in mastocytosis patients with HVA, and it may contribute to predict or confirm these nearly fatal reactions, especially before discontinuing venom immunotherapy in patients who are negative for skin tests or sIgE or display low total IgE levels; in such cases, it also provides evidence on the culprit insect prompting HVA.

Standards and impact of hematopathology in myelodysplastic syndromes (MDS)

The diagnosis, classification, and prognostication of patients with myelodysplastic syndromes (MDS) are usually based on clinical parameters, analysis of peripheral blood and bone marrow smears, and cytogenetic determinants. However, a thorough histologic and immunohistochemical examination of the bone marrow is often required for a final diagnosis and exact classification in these patients. Notably, histology and immunohistology may reveal dysplasia in megakaryocytes or other bone marrow lineages and/or the presence of clusters of CD34-positive precursor cells. In other cases, histology may reveal an unrelated or co-existing hematopoietic neoplasm, or may support the conclusion the patient is suffering from acute myeloid leukemia rather than MDS. Moreover, histologic investigations and immunohistology may reveal an increase in tryptase-positive cells, a coexisting systemic mastocytosis, or bone marrow fibrosis, which is of prognostic significance. To discuss diagnostic algorithms, terminologies, parameters, and specific issues in the hematopathologic evaluation of MDS, a Working Conference involving a consortium of US and EU experts, was organized in June 2010. The outcomes of the conference and resulting recommendations provided by the faculty, are reported in this article. These guidelines should assist in the diagnosis, classification, and prognostication in MDS in daily practice as well as in clinical trials.

How I treat patients with advanced systemic mastocytosis

Advanced systemic mastocytosis (SM) is a rare myeloid neoplasm characterized by uncontrolled accumulation of neoplastic mast cells (MCs) in various organs with consecutive impairment of organ function, drug resistance, and a poor prognosis. Advanced SM may present as smoldering or slowly progressing neoplasm but may also present as rapidly progressing aggressive SM or even as MC leukemia. Approximately half of the patients have an associated hematologic non-MC-lineage disease (SM-AHNMD) or develop an AHNMD over time. Drug resistance may not only result from the KIT mutant D816V that is found in most patients, but also from KIT-independent pro-oncogenic signaling pathways that play a role in disease evolution. In patients with slow progression, advanced SM can often be kept under control for months with interferon-α or 2CdA. By contrast, in rapidly progressing aggressive SM and MC leukemia, even polychemotherapy and hematopoietic stem cell transplantation may fail, which points to the need to develop new drugs and treatment concepts for these patients. In SM-AHNMD, separate treatment plans should be established for the SM component and the AHNMD component of the disease, with recognition that the AHNMD often has to be managed and treated as a secondary and thus a high-risk neoplasm.

Comparative analysis of mutation of tyrosine kinase kit in mast cells from patients with systemic mast cell activation syndrome and healthy subjects

Systemic mast cell activation syndrome is a mast cell disorder characterized by an unregulated increased activation of mast cells leading to a pathologically enhanced release of mediators. Mutations in tyrosine kinase kit which crucially determines mast cell activity have been suggested as a necessary condition for the development of a clinically symptomatic mast cell disease. At the level of mRNA in mast cell progenitor cells of 20 patients with systemic mast cell activation syndrome and of 20 gender- and age-matched healthy volunteers, the tyrosine kinase kit was investigated for genetic alterations by means of RT-PCR and direct sequencing of the amplificates. In mast cells of 13 out of these 20 patients, multiple predominantly novel potential functionally activating point mutations or complex alterations of the mRNA sequence encoding the tyrosine kinase kit were detected. In contrast, in 19 of the 20 healthy subjects, no functionally relevant alterations of c-kit transcripts were detected. The present findings support the idea that the systemic mast cell activation syndrome is a clonal disease most commonly associated with variable activating mutations in the tyrosine kinase kit.

[Systemic mastocytosis--definition of an internal disease]

Systemic mastocytosis comprises disorders characterized by an accumulation of genetically altered mast cells in all organs and tissues due to an increased proliferation rate and reduced apoptosis of those pathologic mast cells. Release of their mediators can effectively influence organ function and can lead to systemic effects without inducing traces in routinely used laboratory parameters or imaging methods. In most cases, little invasive investigations allow diagnosing the disease and, hence, an appropriate therapy consisting of a basic medication with antihistamine and mast cell membrane-stabilizing compounds that should be supplemented, if required, by a medication adapted to individual symptoms, can be initiated. Because of the probably high prevalence of the disorder, systemic mastocytosis should be considered as a differential diagnosis in particular in the case of chronic gastrointestinal complaints such as abdominal pain/discomfort possibly associated with diarrhea, at an early stage.

Clinical, biological, and molecular characteristics of clonal mast cell disorders presenting with systemic mast cell activation symptoms

BACKGROUND

Systemic mast cell activation disorders (MCADs) are characterized by severe and systemic mast cell (MC) mediators-related symptoms frequently associated with increased serum baseline tryptase (sBt).

OBJECTIVE

To analyze the clinical, biological, and molecular characteristics of adult patients presenting with systemic MC activation symptoms/anaphylaxis in the absence of skin mastocytosis who showed clonal (c) versus nonclonal (nc) MCs and to provide indication criteria for bone marrow (BM) studies.

METHODS

Eighty-three patients were studied. Patients showing clonal BM MCs were grouped into indolent systemic mastocytosis without skin lesions (ISMs(-); n = 48) and other c-MCADs (n = 3)-both with CD25(++) BM MCs and either positive mast/stem cell growth factor receptor gene (KIT) mutation or clonal human androgen receptor assay (HUMARA) tests-and nc-MCAD (CD25-negative BM MCs in the absence of KIT mutation; n = 32) and compared for their clinical, biological, and molecular characteristics.

RESULTS

Most clonal patients (48/51; 94%) met the World Health Organization criteria for systemic mastocytosis and were classified as ISMs(-), whereas the other 3 c-MCAD and all nc-MCAD patients did not. In addition, although both patients with ISMs(-) and patients with nc-MCAD presented with idiopathic and allergen-induced anaphylaxis, the former showed a higher frequency of men, cardiovascular symptoms, and insect bite as a trigger, together with greater sBt. Based on a multivariate analysis, a highly efficient model to predict clonality before BM sampling was built that includes male sex (P = .01), presyncopal and/or syncopal episodes (P = .009) in the absence of urticaria and angioedema (P = .003), and sBt >25 microg/L (P = .006) as independent predictive factors.

CONCLUSIONS

Patients with c-MCAD and ISMs(-) display unique clinical and laboratory features different from nc-MCAD patients. A significant percentage of c-MCAD patients can be considered as true ISMs(-) diagnosed at early phases of the disease.

Phenotypic heterogeneity, novel diagnostic markers, and target expression profiles in normal and neoplastic human mast cells

Mast cells (MC) are specialized immune cells that play a key role in anaphylactic reactions. Growth, differentiation, and function of these cells are regulated by a complex network of cytokines, surface receptors, signaling molecules, the microenvironment, and the genetic background. A number of previous and more recent data suggest that MC are heterogeneous in terms of cytokine-regulation, expression of cytoplasmic and cell surface antigens, and response to ligands. MC heterogeneity is often organ-specific and is considered to be related to MC plasticity, disease-associated factors, and the maturation stage of the cells. The stem cell factor (SCF) receptor KIT (CD117) is expressed on all types of MC independent of maturation and activation-status. In systemic mastocytosis (SM), KIT is often expressed in MC in a mutated and constitutively activated form. In these patients, MC aberrantly display CD2 and CD25, diagnostic markers of neoplastic MC in all SM variants. In advanced SM, MC co-express substantial amounts of CD30, whereas CD2 expression on MC may be decreased compared to indolent SM. Other surface molecules, such as CD63 or CD203c, are overexpressed on neoplastic MC in SM, and are further upregulated upon cross-linking of the IgE receptor. Some of the cell surface antigens expressed on MC or their progenitors may serve as therapeutic targets in the future. These targets include CD25, CD30, CD33, CD44, and CD117/KIT. The current article provides an overview on cell surface antigens and target receptors expressed by MC in physiologic and reactive tissues, and in patients with SM, with special reference to phenotypic heterogeneity and clinical implications.

Gastrointestinal involvement and manifestations in systemic mastocytosis

Mastocytosis is a rare and heterogeneous disease characterized by various biological and clinical features with different prognosis and treatments. The disease is usually divided into 2 categories: a pure cutaneous and a systemic disease. Clinical features can be related to mast cells' mediators release or to pathological mast cells infiltration. The diagnosis of mastocytosis is based on clinical, biological, histological, and molecular international criteria. Among all manifestations of the disease, gastrointestinal (GI) symptoms are common and can significantly impair the quality of life. The aim of this article is to review the data regarding GI involvement in mastocytosis. Articles dealing with clinical, pathophysiological, and therapeutic aspects of mastocytosis GI tract involvement were searched for using PubMed. GI manifestations in mastocytosis are reviewed. Pathogenesis of GI symptoms in systemic mastocytosis and their treatment are critically discussed. The most frequent GI symptoms are abdominal pain, diarrhea, nausea, and vomiting. GI lesions may involve all the digestive tract, from the esophagus to the rectum. The histological diagnosis of GI involvement is difficult. The treatment of GI symptoms aims to prevent and limit mast cells degranulation and/or its consequences and more rarely to control tumoral mast cells infiltration. The high prevalence of GI symptoms in mastocytosis and their important functional impact deserves better characterization and treatment in order to improve patients' quality of life. Diagnosis of mastocytosis GI manifestations should be evoked in the case of unexplained severe GI disorders.

Contemporary challenges in mastocytosis

Mastocytosis denotes a wide range of disorders characterized by having abnormal growth and accumulation of mast cells. Mast cells contain histamine and other inflammatory mediators, which have diverse actions within the body, and play crucial roles in acquired and innate immunity. The diverse actions of these inflammatory mediators can lead to puzzling symptoms in individuals with mastocytosis. These symptoms can include flushing, pruritus, nausea, vomiting, abdominal pain, diarrhea, vascular instability, and headache. These clinical features generally divide into cutaneous and systemic manifestations, giving rise to the two divisions of mastocytosis: cutaneous mastocytosis (CM) and systemic mastocytosis. CM has a highly favorable clinical prognosis. Systemic mastocytosis has a range of severity, with the milder forms often remaining chronic conditions, while the severe forms have rapid complex courses with poor prognoses. Generally, treatment is aimed at avoiding mast cell degranulation, inhibiting the actions of the constitutive mediators released by mast cells and, in severe cases, cytoreductive and polychemotherapeutic agents. Behavioral intervention includes avoidance of triggers, such as heat, cold, pressure, exercise, sunlight, and strong emotions. Treatment for released histamine and other inflammatory mediators includes H1 antihistamines, H2 antihistamines, proton pump inhibitors, anti-leukotriene agents, and injectible epinephrine (for possible anaphylaxis). For severe cases, treatment includes cytoreductive agents (interferon alpha, glucocorticoids, and cladribine) and polychemotherapeutic agents (daunomycin, etoposide, and 6-mercaptopurine). For very specific and severe cases, tyrosine kinase inhibitors, imatinib and midostaurine, have shown promise.

In vitro and in vivo growth-inhibitory effects of cladribine on neoplastic mast cells exhibiting the imatinib-resistant KIT mutation D816V

OBJECTIVE

In most patients with systemic mastocytosis (SM), including aggressive SM (ASM) and mast cell (MC) leukemia (MCL), neoplastic cells express the oncogenic KIT mutation D816V, which confers resistance to imatinib. Cladribine (2CdA) is a nucleoside analog that has been introduced as a promising agent for treatment of advanced SM.

MATERIALS AND METHODS

We examined the in vitro effects of 2CdA on growth of neoplastic MC, and the in vivo effects of 2CdA (0.13 mg/kg/day intravenously, days 1-5; three to eight cycles) in seven patients with advanced SM.

RESULTS

Cladribine was found to inhibit growth of primary MC and the MC line HMC-1 in a dose-dependent manner, with lower IC(50) values recorded in HMC-1.2 cells harboring KIT D816V (IC(50): 10 ng/mL) compared to HMC-1.1 cells lacking KIT D816V (IC(50): 300 ng/mL). In two patients with progressive smoldering SM, 2CdA produced a long-lasting response with a sustained decrease in serum tryptase levels, whereas in patients with progressive ASM or MCL, 2CdA showed little if any effects. The drug was well-tolerated in most cases. However, one patient developed a massive generalized purulent long-lasting skin rash. The antiproliferative effects of 2CdA on MC were found to be associated with morphologic signs of apoptosis and caspase cleavage. Cladribine did not counteract the kinase activity of KIT D816V or KIT-downstream signaling molecules.

CONCLUSIONS

Cladribine may be a promising agent for treatment of progressive smoldering KIT D816V(+) SM. In rapidly progressing ASM or MCL, additional or alternative drugs are required to induce long-lasting antineoplastic effects.

High frequency of concomitant mastocytosis in patients with acute myeloid leukemia exhibiting the transforming KIT mutation D816V

The KIT mutation D816V is associated with autonomous growth of mast cells (MC) and is detectable in most patients with systemic mastocytosis (SM), including cases with associated hematologic non-MC-lineage disease (AHNMD). Recently, KIT D816V was reported to be expressed in patients with acute myeloid leukemia (AML). However, it was not clarified whether these patients have co-existing occult SM. We investigated neoplastic cells in 101 patients with AML for expression of KIT D816V. In 7/101 patients (6.9%), KIT D816V was detectable. After a thorough histologic, molecular, and biochemical analysis, all 7 cases were found to have an associated SM, leading to the final diagnosis SM-AML. Microdissected tryptase+ MC displayed KIT D816V in all patients tested, whereas CD34+ blasts exhibited KIT D816V in only 2/4 patients. In one AML patient, SM without KIT D816V was detected. In all other patients, no associated SM was found, and leukemic blasts were negative for KIT D816V. In summary, our data show that KIT D816V in AML is highly associated with co-existing SM (SM-AML). Moreover, our data show that AML blasts may lack this transforming target-mutant, which may be important when considering the use of KIT D816V-targeting drugs for treatment of patients with KIT D816V-positive AML.

Variable presence of KITD816V in clonal haematological non-mast cell lineage diseases associated with systemic mastocytosis (SM-AHNMD)

In a substantial number of patients with systemic mastocytosis (SM), an associated clonal haematological non-mast cell lineage disease (AHNMD) is detectable. Although most of these patients display KIT mutations, especially KIT(D816V), little is known about their exact frequency and their distribution in AHNMD subtypes. We examined 48 patients with SM-AHNMD for the presence of mutant KIT in the SM and AHNMD components of the disease. Mast cells and AHNMD cells were obtained from immunostained bone marrow sections by laser microdissection and examined by melting point analysis of nested-PCR products. KIT(D816V) was found in AHNMD cells in the vast majority of patients with SM-chronic myelomonocytic leukaemia (CMML, 89%). Unexpectedly, KIT(D816V) was far less frequently detectable in AHNMD cells in patients with SM-myeloproliferative neoplasm (MPN, 20%) and SM-acute myeloid leukaemia (AML, 30%). None of the patients with lymphoproliferative AHNMDs displayed KIT codon 816 mutations in AHNMD cells (0/8). In FIP1L1/PDGFRA-positive chronic eosinophilic leukaemia (CEL), neither the SM nor the CEL component of the disease exhibited the KIT mutation. Our findings demonstrate that KIT codon 816 mutations are variably present in AHNMD cells in patients with SM-AHNMD, depending on the subtype of AHNMD. The high frequency of KIT(D816V) in neoplastic mast cells and leukaemic myelomonocytic cells in SM-CMML may point to a common precursor in these patients, and may have implications for the biology of the disease and the development of KIT-targeting therapies.

Current approaches to the diagnosis and treatment of systemic mastocytosis

OBJECTIVE

To review the clinical manifestations of mastocytosis and examine the recommended diagnostic procedures and therapeutic options available for the treatment of this condition.

DATA SOURCES

PubMed searches were performed for articles published regarding presentation and classification of mastocytosis and the diagnostic criteria and treatment options for this condition using the keywords mastocytosis, clinical features, World Health Organization diagnostic criteria, management, pathogenesis, and urticaria pigmentosa. Retrieved articles were surveyed for additional citations.

STUDY SELECTION

Articles were reviewed for relevance to the study objectives, and more recent articles were preferentially included. Prospective studies were preferentially included when available.

RESULTS

Mastocytosis is a heterogeneous disorder that results from clonal mast cell proliferation. Symptoms are typically limited to the skin in the pediatric population, requiring only symptomatic treatment with spontaneous resolution by puberty. Disease course in adults ranges from minimally symptomatic in most to highly aggressive but tends to be persistent. Symptoms can be protean and nonspecific. The mainstay of treatment consists of avoidance of triggers of mast cell degranulation and symptom-based therapy.

CONCLUSIONS

Mastocytosis should be suspected in patients who present with a constellation of symptoms, including flushing, abdominal pain, diarrhea, unexplained syncope, and classic urticaria pigmentosa lesions. Diagnosis should be established by a bone marrow biopsy in all adults. Staging should be performed to assess disease burden and evidence of end-stage organ damage. Patients should be offered symptom-based treatment and cytoreductive therapy only for aggressive systemic mastocytosis or an associated hematologic malignant neoplasm.

Mastocytosis

Mastocytosis is characterized by pathologic accumulation and activation of mast cells in tissues and organs. Although the classification for mastocytosis and diagnostic criteria are well accepted, there remains a need to define standards for the application of diagnostic tests, clinical evaluations, and responses to treatment. The objective of this article was to make an extensive literature review, providing comprehensive knowledge about the etiopathological and pathophysiological mechanisms, with a special emphasis on diagnosis, classification and treatment of mastocytosis, promoting continued medical education.

A critical reappraisal of treatment response criteria in systemic mastocytosis and a proposal for revisions

Mast cell disease (MCD) is a hematopoietic stem cell neoplasm that is associated with infiltration of one or more organs with cytologically abnormal mast cells (MC). MCD is frequently but not always associated with a KIT mutation and, in some cases, is associated with clonal expansion of non-MC lineage cells. In adults, there is almost always MC infiltration of the bone marrow, which is a cardinal feature of systemic mastocytosis (SM). While, as members of the wider community of physician scientists, we recognize the contribution of the current consensus treatment response criteria for SM, as individuals with more than average clinical experience in SM, we would like to point out their limitations and engage in a constructive discussion that will hopefully lead to a consideration for revisions. We present here an alternative proposal for treatment response assessments we believe is more objective, reproducible, and importantly, SM-subtype specific, given the recent progress in our understanding of the natural history of this disease. We believe this proposal is timely given the prospects for new clinical trials in SM, and the related regulatory aspects of new drug approval that are currently not adequately addressed. The intent of this exercise is not to undermine the complexity of the disease or previous work by other investigators, but to come up with ideas for response criteria that are more practical and consider meaningful patient outcome.

Recent advances in mast cell clonality and anaphylaxis

Clonal expansion of mast cells carrying the D816V c-kit mutation results in mastocytosis. Recent studies identified the presence of clonal mast cells carrying this mutation in patients with anaphylaxis without classic diagnostic findings of systemic mastocytosis.

Cytoreductive therapy in 108 adults with systemic mastocytosis: Outcome analysis and response prediction during treatment with interferon-alpha, hydroxyurea, imatinib mesylate or 2-chlorodeoxyadenosine

Cytoreductive therapy in systemic mastocytosis (SM) includes several drugs whose individual merit has not been well characterized. We retrospectively studied 108 Mayo Clinic patients who met the 2008 WHO diagnostic criteria for SM and received at least one cytoreductive drug. The numbers of patients who were evaluable for response to treatment with interferon-alpha with or without prednisone (IFN-alpha), hydroxyurea (HU), imatinib mesylate (IM) or 2-chlorodeoxyadenosine (2-CdA) were 40, 26, 22, and 22, respectively. The corresponding overall (major) response rates, according to recently published consensus criteria, were 53% (18%), 19% (0%), 18% (9%), and 55% (37%). The respective overall response rates in indolent SM, aggressive SM and SM associated with another clonal hematological nonmast cell lineage disease (SM-AHNMD) were 60%, 60%, 45% for IFN-alpha, 0, 0, 21% for HU, 14%, 50%, 9% for IM and 56%, 50%, 55% for 2-CdA. The absence of mast cell mediator release symptoms in IFN-alpha-treated patients and presence of circulating immature myeloid cells in 2-CdA-treated patients predicted inferior response. TET2 mutational status did not influence treatment response. Although the major response rates with these four cytoreductive agents were still suboptimal and HU was mainly used in patients with SM-AHNMD, the current study favors 2-CdA or IFN-alpha as first-line current therapy in SM and identifies patients who are likely to respond to such therapy.

Prognostically relevant breakdown of 123 patients with systemic mastocytosis associated with other myeloid malignancies

The prognostic heterogeneity of the World Health Organization category of “systemic mastocytosis with associated clonal hematologic nonmast cell lineage disease” (SM-AHNMD) has not been systematically validated by primary data. Among 138 consecutive cases with SM-AHNMD, 123 (89%) had associated myeloid neoplasm: 55 (45%) myeloproliferative neoplasm (SM-MPN), 36 (29%) chronic myelomonocytic leukemia, 28 (23%) myelodysplastic syndrome (SM-MDS), and 4 (3%) acute leukemia. Of the myeloid subgroups, SM-MPN displayed a 2- to 3-fold better life expectancy (P = .003), whereas leukemic transformation was more frequent in SM-MDS (29%; P = .02). The presence of eosinophilia, although prevalent (34%), was prognostically neutral, and the overall results were not affected by exclusion of FIP1L1-PDGFRA-positive cases. We conclude that it is clinically more useful to consider specific entities, such as SM-MPN, systemic mastocytosis with chronic myelomonocytic leukemia, SM-MDS, and systemic mastocytosis with-acute leukemia, rather than their broad reference as SM-AHNMD.

Identification of proapoptotic Bim as a tumor suppressor in neoplastic mast cells: role of KIT D816V and effects of various targeted drugs

Systemic mastocytosis (SM) is a myeloid neoplasm involving mast cells (MCs) and their progenitors. In most cases, neoplastic cells display the D816V-mutated variant of KIT. KIT D816V exhibits constitutive tyrosine kinase (TK) activity and has been implicated in increased survival and growth of neoplastic MCs. Recent data suggest that the proapoptotic BH3-only death regulator Bim plays a role as a tumor suppressor in various myeloid neoplasms. We found that KIT D816V suppresses expression of Bim in Ba/F3 cells. The KIT D816-induced down-regulation of Bim was rescued by the KIT-targeting drug PKC412/midostaurin. Both PKC412 and the proteasome-inhibitor bortezomib were found to decrease growth and promote expression of Bim in MC leukemia cell lines HMC-1.1 (D816V negative) and HMC-1.2 (D816V positive). Both drugs were also found to counteract growth of primary neoplastic MCs. Furthermore, midostaurin was found to cooperate with bortezomib and with the BH3-mimetic obatoclax in producing growth inhibition in both HMC-1 subclones. Finally, a Bim-specific siRNA was found to rescue HMC-1 cells from PKC412-induced cell death. Our data show that KIT D816V suppresses expression of proapoptotic Bim in neoplastic MCs. Targeting of Bcl-2 family members by drugs promoting Bim (re)-expression, or by BH3-mimetics such as obatoclax, may be an attractive therapy concept in SM.

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

BACKGROUND

Pediatric onset mastocytosis usually presents as urticaria pigmentosa; and less often as diffuse cutaneous mastocytosis. While the literature indicates that disease often resolves, there has been a move to more aggressive therapy for mastocytosis early in life. We addressed the long term prognosis of pediatric-onset disease by examining 17 children with mastocytosis which we had reported on in 1989 [1].

PROCEDURE

We successfully contacted 15 of these patients and data was collected regarding their clinical status. Original bone marrow specimens were re-stained, re-examined, and correlated with disease outcome using consensus criteria. Three of five patients with persistent disease underwent repeat bone marrow biopsies.

RESULTS

There was complete regression of disease as defined by cutaneous findings and symptoms (clinical disease severity) in 10 of 15 patients (67%). Three patients had major (20%) and two had partial regression of disease (13%). Repeat marrow examinations on three patients with persistent disease documented systemic mastocytosis based on marrow findings in one patient who had partial regression of disease and was the only patient with initial morphologic evidence of systemic disease. Of the remaining two patients, one demonstrated partial regression and the other major regression of disease; and neither had evidence of systemic mastocytosis.

CONCLUSION

This study demonstrates that initial bone marrow biopsies were prognostic in that those without evidence of systemic disease experienced disease regression; and that the long term prognosis for children managed symptomatically with mastocytosis is highly encouraging.

Elevated tryptase levels selectively cluster in myeloid neoplasms: a novel diagnostic approach and screen marker in clinical haematology

BACKGROUND

Recent data suggest that tryptase, a mast cell enzyme, is expressed in neoplastic cells in myeloid leukaemias. In several of these patients, increased serum tryptase levels are detectable.

MATERIALS AND METHODS

We have determined serum tryptase levels in 914 patients with haematological malignancies, including myeloproliferative disorders (n = 156), myelodysplastic syndromes (MDS, n = 241), acute myeloid leukaemia (AML, n = 317), systemic mastocytosis (SM, n = 81), non-Hodgkin's lymphoma (n = 59) and acute lymphoblastic leukaemia (n = 26). Moreover, tryptase was measured in 136 patients with non-neoplastic haematological disorders, 102 with non-haematological disorders and 164 healthy subjects.

RESULTS

In healthy subjects, the median serum tryptase was 5.2 ng mL(-1). Elevated serum tryptase levels were found to cluster in myeloid neoplasm, whereas almost all patients with lymphoid neoplasms exhibited normal tryptase. Among myeloid neoplasms, elevated tryptase levels (> 15 ng mL(-1)) were recorded in > 90% of patients with SM, 38% with AML, 34% with CML and 25% with MDS. The highest tryptase levels, often > 1000 ng mL(-1), were found in advanced SM and core-binding-factor leukaemias. In most patients with non-neoplastic haematological disorders and non-haematological disorders analysed in our study, tryptase levels were normal, the exception being a few patients with end-stage kidney disease and helminth infections, in whom a slightly elevated tryptase was found.

CONCLUSIONS

In summary, tryptase is a new diagnostic marker of myeloid neoplasms and a useful test in clinical haematology.

The problem of anaphylaxis and mastocytosis

Mastocytosis is a rare disease characterized by an elevated whole body mast cell number. Anaphylaxis is a severe, generalized hypersensitivity reaction with rapid onset. The problem of anaphylaxis and mastocytosis is due to strongly increased mediator release from the elevated mast cell number during allergic reactions. This explains the much higher prevalence of anaphylaxis in mastocytosis than in the general population and its severe and sometimes fatal course. Because of the increased risk of anaphylaxis in mastocytosis, all patients with severe or recurrent anaphylaxis should be analyzed for underlying mastocytosis by estimation of baseline serum tryptase. If this is elevated, patients also should be tested via skin examination for cutaneous mastocytosis and with a bone marrow biopsy. All patients with mastocytosis and anaphylaxis must be instructed about avoiding the responsible elicitors and should carry an emergency kit with adrenaline for self-application. In mastocytosis patients with anaphylaxis due to Hymenoptera stings, venom immunotherapy is recommended for life.

Unexplained and prolonged perioperative hypotension after orthotopic liver transplantation: undiagnosed systemic mastocytosis

Arterial vasodilation is common in end-stage liver disease, and systemic hypotension often may develop, despite an increase in cardiac output. During the preparation for and the performance of orthotopic liver transplantation, expected and transient hypotension may be caused by induction agents, anesthetic agents, liver mobilization, or venous clamping. A mild decrease of the already low systemic vascular resistance is often observed, and intermittent use of short-acting agents for vasopressor support is not uncommon. In this report, we describe a patient with unexpected and prolonged hypotension due to vasodilation during and after orthotopic liver transplantation. The preoperative end-stage liver disease evaluation, intraoperative events, and intensive care unit course were reviewed, and no cause for the vasodilation and prolonged hypotension was evident. The explant pathology report was later available and showed systemic mastocytosis. We hypothesize that the unexpected hypotension and vasodilation were caused by mast cell degranulation and its systemic effects on arterial tone.

Physiological and pathophysiological functions of intestinal mast cells

The normal gastrointestinal (GI) mucosa is equipped with mast cells that account for 2-3% of lamina propria cells under normal conditions. Mast cells are generally associated with allergic disease, and indeed, food allergy that manifests in the GI tract is usually mast cell dependent. On the other hand, mast cells have a number of physiological functions in the GI tract, namely regulatory functions such as control of blood flow and coagulation, smooth muscle contraction and peristalsis, and secretion of acid, electrolytes, and mucus by epithelial cells. One of the most intriguing functions of intestinal mast cells is their role in host defense against microbes like bacteria, viruses, or parasites. Mast cells recognize microbes by antibody-dependent mechanisms and through pattern-recognition receptors. They direct the subsequent immune response by attracting both granulocytes and lymphocytes to the site of challenge via paracrine cytokine release. Moreover, mast cells initiate, by releasing proinflammatory mediators, innate defense mechanisms such as enhanced epithelial secretion, peristalsis, and alarm programs of the enteric nervous This initiation can occur in response to a primary contact to the microbe or other danger signals, but becomes much more effective if the triggering antigen reappears and antibodies of the IgE or IgG type have been generated in the meantime by the specific immune system. Thus, mast cells operate at the interface between innate and adaptive immune responses to enhance the defense against pathogens and, most likely, the commensal flora. In this respect, it is important to note that mast cells are directly involved in controlling the function of the intestinal barrier that turned out to be a crucial site for the development of infectious and immune-mediated diseases. Hence, intestinal mast cells perform regulatory functions to maintain tissue homeostasis, they are involved in host defense mechanisms against pathogens, and they can induce allergy once they are sensitized against foreign antigens. The broad spectrum of functions makes mast cells a fascinating target for future pharmacological or nutritional interventions.

Ureteral stones due to systemic mastocytosis: diagnostic and therapeutic characteristics

Urolithiasis is expected to cause a considerable complication in patients with systemic mastocytosis. The aim of the present report is to demonstrate that due to pathological activation and irritability of mast cells, special features in the diagnostic investigation and therapy of urolithiasis have to be considered in patients with systemic mastocytosis. The clinical presentation, diagnostic investigation and therapeutic procedure of urolithiasis in a patient with systemic mastocytosis are described. Urolithiasis may be a significant complication of systemic mastocytosis. Non-contrast CT is the main tool for diagnosing urolithiasis after a detailed history and clinical exam. Patients with systemic mastocytosis should receive a premedication composed of a glucocorticoid and H(1)- and H(2)-histamine receptor antagonists. An increased vulnerability of mucosal tissues is expected in patients with systemic mastocytosis that may limit the options of operative and postoperative therapy. Opioids should be used cautiously for analgesia in patients with systemic mastocytosis.

CD203c is overexpressed on neoplastic mast cells in systemic mastocytosis and is upregulated upon IgE receptor cross-linking

The ectoenzyme E-NPP3 (CD203c) has recently been identified as a novel activation-linked cell surface antigen on basophils. In the present study, we examined expression of CD203c on normal mast cells (MC)and bone marrow (bm) MC derived from 85 patients with systemic mastocytosis (SM), including cases with indolent SM (ISM, n=72), SM with associated clonal hematologic non-MC-lineage disease (SM-AHNMD, n=6), aggressive SM (ASM, n=3), and mast cell leukemia (MCL, n=4). Surface expression of CD203c was analyzed by multicolor flow cytometry. In patients with SM, bm MC expressed significantly higher amounts of CD203c compared to normal bm MC (median MFI in controls: 260 versus median MFI in SM: 516, p<0.05). Slightly lower amounts of CD203c were detected on MC in SM-AHNMD and ASM compared to ISM. To demonstrate CD203c expression in MC at the mRNA level, neoplastic MC were highly enriched by cell sorting, and were found to express CD203c mRNA in RT-PCR analysis. Cross-linking of the IgE receptor on MC resulted in a substantial upregulation of CD203c, whereas the KIT-ligand stem cell factor (SCF) showed no significant effects. In conclusion, CD203c is a novel activation-linked surface antigen on MC that is upregulated in response to IgE receptor cross-linking and is overexpressed on neoplastic MC in patients with SM.