Systemic mastocytosis with extensive polypoid lesions in the intestines; successful treatment with interferon-alpha

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

OVERVIEW

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

DIAGNOSIS

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

RISK STRATIFICATION

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

MANAGEMENT

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

Precision Medicine in Systemic Mastocytosis

Mastocytosis is a rare hematological neoplasm characterized by the proliferation of abnormal clonal mast cells (MCs) in different cutaneous and extracutaneous organs. Its diagnosis is based on well-defined major and minor criteria, including the pathognomonic dense infiltrate of MCs detected in bone marrow (BM), elevated serum tryptase level, abnormal MCs CD25 expression, and the identification of KIT D816V mutation. The World Health Organization (WHO) classification subdivides mastocytosis into a cutaneous form (CM) and five systemic variants (SM), namely indolent/smoldering (ISM/SSM) and advanced SM (AdvSM) including aggressive SM (ASM), SM associated to hematological neoplasms (SM-AHN), and mast cell leukemia (MCL). More than 80% of patients with SM carry a somatic point mutation of KIT at codon 816, which may be targeted by kinase inhibitors. The presence of additional somatic mutations detected by next generation sequencing analysis may impact prognosis and drive treatment strategy, which ranges from symptomatic drugs in indolent forms to kinase-inhibitors active on KIT. Allogeneic stem cell transplant (SCT) may be considered in selected SM cases. Here, we review the clinical, diagnostic, and therapeutic issues of SM, with special emphasis on the translational implications of SM genetics for a precision medicine approach in clinical practice.

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

OVERVIEW

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

DIAGNOSIS

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

RISK STRATIFICATION

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

MANAGEMENT

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

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

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

DIAGNOSIS

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

MANAGEMENT

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

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

DISEASE OVERVIEW

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

DIAGNOSIS

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

RISK STRATIFICATION

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

MANAGEMENT

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

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.

Systemic mastocytosis in adults: 2013 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

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

DIAGNOSIS

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

RISK STRATIFICATION

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

MANAGEMENT

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

INVESTIGATIONAL DRUGS

Dasatinib's in vitro anti- KITD816V activity has not translated into significant therapeutic activity in most SM patients. In contrast, recently updated data confirms Midostaurin's significant anti-MC activity in patients with advanced SM.

Systemic mastocytosis in adults: 2012 Update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

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

DIAGNOSIS

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

RISK STRATIFICATION

The prognostic relevance of the 2008 World Health Organization (WHO) classification of SM has recently been confirmed. Classification of SM patients into indolent (SM), aggressive SM (ASM), SM associated with a clonal non-MC lineage disease (SM-AHNMD) and mast cell leukemia (MCL) subgroups is a useful first step in establishing prognosis.

MANAGEMENT

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

INVESTIGATIONAL DRUGS

Dasatinib's in vitro anti-KITD816V activity has not translated into significant therapeutic activity in most SM patients. In contrast, preliminary data suggest that Midostaurin may produce significant decreases in MC burden in some patients.

Systemic mastocytosis in adults: 2011 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

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

DIAGNOSIS

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

RISK STRATIFICATION

The prognostic relevance of the 2008 World Health Organization (WHO) classification of SM has recently been confirmed. Classification of SM patients into indolent (SM), aggressive SM (ASM), SM associated with a clonal non-MC lineage disease (SM-AHNMD), and mast cell leukemia (MCL) subgroups is a useful first step in establishing prognosis.

RISK-ADAPTED THERAPY

SM treatment is generally palliative. ISM patients have a normal life expectancy and receive symptom-directed therapy; infrequently, cytoreductive therapy may be indicated for refractory symptoms. ASM patients have disease-related organ dysfunction; interferon-α (±corticosteroids) can control dermatological, hematological, gastrointestinal, skeletal, and mediator-release symptoms, but is hampered by poor tolerability. Similarly, cladribine has broad therapeutic activity, with particular utility when rapid MC debulking is indicated; the main toxicity is myelosuppression. Imatinib has a therapeutic role in the presence of an imatinib-sensitive KIT mutation or in KITD816-unmutated patients. Treatment of SM-AHNMD is governed primarily by the non-MC neoplasm; hydroxyurea has modest utility in this setting. Dasatinib's in vitro anti- KITD816V activity has not translated into significant therapeutic activity in most SM patients. In contrast, preliminary data suggest that Midostaurin may produce significant decreases in MC burden in some patients.

Neurotransmitters excreted in the urine as biomarkers of nervous system activity: validity and clinical applicability

Strategies for managing the nervous system are numerous while methods of evaluating the nervous system are limited. Given the physiological importance of neurotransmitters as signaling molecules in the nervous system, the measurement of neurotransmitters has significant potential as a clinical tool. Of all the biological fluids that can be utilized, urinary neurotransmitter testing, due to its stability, sensitivity, and non-invasiveness, is the desired method to analyze nervous system function. Increasing use of this technology in a clinical setting demands a review of its feasibility, utility, and clinical value. We review the current body of literature pertaining to the mechanism of neurotransmitter transport across the blood-brain barrier as well as neurotransmitter filtration and excretion by the kidneys. In addition, this review summarizes the historical use of urinary neurotransmitter assessment to diagnose pheochromocytoma. Early research also correlated urinary assessment of neurotransmitters to various clinical symptoms and treatments of which we present research only for depression, ADHD, and inflammation because of the abundant amount of research in these areas. Finally, we review the limitations and challenges of urinary neurotransmitter testing. Taken together, evidence suggests that neurotransmitters excreted in the urine may have a place in clinical practice as a biomarker of nervous system function to effectively assess disturbances and monitor treatment efficacy.

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.

Aggressive systemic mastocytosis complicated by protein-losing enteropathy

A 46-year-old woman was admitted to the hospital with complaints of chronic diarrhoea, vomiting and severe muscle weakness. Clinical examination showed a lethargic, malnourished, dehydrated patient with ascites and bilateral leg oedema. Laboratory evaluation revealed mild normochromic normocytic anaemia and severe hypoproteinaemia with hypoalbuminaemia. Upper gastrointestinal endoscopy showed a thickened, friable duodenal mucosa with multiple erosions. Colonoscopy revealed nodular, pseudopolypoid lesions with patchy erosions in the left hemicolon. Haematoxylin-eosin stained sections from biopsies of endoscopically abnormal bowel segments showed multi-focal aggregates of large, histiocyte-like cells with abundant pale cytoplasm in the lamina propria. These cells were negative on PAS, Ziehl-Neelsen, Giemsa and toluidine blue stains. Their immunophenotype was CD68 (+), c-kit/CD117 (+) and mast cell tryptase (+), which is consistent with mast cells. A trephine biopsy showed diffuse replacement of the bone marrow by atypical, monomorphic, frequently spindle-shaped mast cells. No associated haematopoietic malignancy was detected. The final diagnosis was aggressive systemic mastocytosis with involvement of the gastrointestinal tract complicated by protein-losing enteropathy. This association has not been reported previously. The patient has been treated with prednisolone and interferon-alpha and has since recovered.

Interferon treatment for hypereosinophilic syndromes and systemic mastocytosis

Hypereosinophilic syndromes (HES) and systemic mastocytosis (SMCD) are heterogeneous disorders with clinical symptoms from local and remote effects of excessive proliferation of eosinophils and mast cells, respectively. Interferon alpha (IFN-alpha), alone or in combination with other medications, can be a useful, and at times life-saving, treatment for patients with HES. Receptors for IFN-alpha are present on eosinophils, and clinical benefits are due to its effect on eosinophil proliferation, migration, activation, and survival. These effects are likely mediated through multiple pathways including, but not limited to, inhibition of eosinophil colony-forming cells, upregulation of IFN-gamma synthesis, and inhibition of production of eosinophil-active cytokines by T cells, mast cells, and mononuclear cells. IFN-alpha has been life-saving for patients with intractable HES that were resistant to prednisone, hydroxyurea, and other agents. Resistance to the eosinopenic effect of IFN-alpha does not develop and the dose of IFN-alpha necessary to maintain control of eosinophilia often decreases with time. The combination of IFN-alpha and hydroxyurea is very useful and allows dosage reduction of IFN-alpha and better control of hypereosinophilia than with either agent alone. The efficacy of IFN-alpha for treatment of SMCD has been more difficult to establish, with both favorable and unfavorable results reported. The disparate results may have resulted from the small number of patients with SMCD treated with IFN-alpha, the use of various criteria for a "successful" treatment outcome, short duration of treatment and follow-up, and the use of modest dosages. In reported series, side effects from IFN-alpha have frequently been dose-limiting. IFN-alpha improves many of the clinical symptoms of SMCD including dermatological, hematological, gastrointestinal, and systemic symptoms associated with histamine release. IFN-alpha has a beneficial effect on skeletal symptoms because of its ability to increase bone density and reduce painful episodes from vertebral fractures. No consistent improvement in bone marrow infiltration by mast cells has been demonstrated except in a recent study employing high dosages of IFN-alpha. A beneficial effect from the combination of IFN-alpha and prednisone has been reported for several patients, suggesting that combined use of these two medications may provide synergism in treatment outcomes.

Management of patients with systemic mastocytosis: review of M. D. Anderson Cancer Center experience

Mastocytosis is characterized by mast cell proliferation that may be limited to the skin (cutaneous mastocytosis) or may involve one or more extracutaneous organs, e.g., the bone marrow (systemic mastocytosis; SM). This study objective is to evaluate the features and outcome of patients referred to M. D. Anderson Cancer Center (MDACC) with SM. A search of the MDACC database from 1944 to 2002 was conducted for patients with SM and review of their clinical charts. Eighteen patients with mastocytosis were identified in the MDACC database; 15 (11 males and 4 females) had SM and available information. Two had associated myelodysplastic syndrome (MDS), and one had acute myeloid leukemia (AML). The median age was 58 years (range 31-80). Nine patients were treated with subcutaneous interferon-alpha, and only 1 experienced temporary control of the disease. Three of these patients were then treated with imatinib mesylate: transient improvement was noted in two patients. One patient underwent stem cell transplantation as first therapy and achieved complete remission; this patient had associated MDS and is now in complete remission for 8 years. The patient with associated AML was treated with high-dose cytarabine and idarubicin; he has been in complete remission for 16 months. One patient was treated with induction chemotherapy consisting of high-dose cytarabine and 2CDA but expired due to sepsis. Three patients received symptomatic therapy only; these were the only 3 patients who presented with normal blood counts. SM is rare and has no effective standard of care. Collaboration among academic centers to accrue enough patients to evaluate novel therapeutic strategies is needed.

Interest of interferon alpha in systemic mastocytosis. The French experience and review of the literature

Systemic mastocytosis (SM) are defined by an abnormal growth and accumulation of mast cells in bone marrow and/or other extracutaneous organs. There is currently no cure for this disease. Because of similarities and/or association of mastocytosis with myeloproliferative disorders, interferon alpha has been tested but with contradictory reported results. A first prospective multicenter phase II trial was then started in France. From 1994 to 1997, 20 adult patients with confirmed bone marrow involvement received interferon alpha-2b for at least 6 months, (from 1 million U per day up to 5 million U/m(2)/day). Thirteen patients who presented systemic and/or specific cutaneous manifestations, demonstrated objective responses: seven (35%) were partial, six (30%) minor but no complete response could be observed at the time of analysis. The bone marrow remained unchanged in 12/13. Thus, interferon should be offered to patients with severe systemic manifestations, who have not responded to symptomatic therapies, even in case of non-aggressive mastocytosis, with or without corticosteroids the first weeks. Long-term therapy should be offered to patients with initial positive response. To control more aggressive SM or mastocytosis associated with clonal hematologic non-mast cell lineage or leukaemia mast cell, other chemotherapeutic regimens should be proposed like Cladribine (2-chlorodeoxyadenosine, 2-CDA) or polychemotherapies including interferon as it is being tested in France in a new multicentric protocol, coordinated by the association AFIRMM, with interferon and oral cytarabine.

[Treatment of systemic mastocytosis]

BACKGROUND

Systemic mastocytosis is a rare disease, characterized by mast cells proliferation in various organs. Two types of clinical manifestations can be distinguished: those related to mast cells mediators release and those related to tumoral proliferation involving different organs, these later defining aggressive systemic mastocytosis. Until recently, treatment was mainly symptomatic, without anti tumoral effect.

RECENT FACTS

These last years, advances have been made in the understanding of the disease with the discovery of the c-kit oncogene mutation and the approach of the disease as a myeloproliferative disorder.

PERSPECTIVES

Based on experiences acquired in the treatment of this kind of disorders, evaluation of new therapeutics, such as cladribine or combination of interferon-alpha and cytarabine is in progress. At least, tyrosine kinase inhibitors, a new family of molecules, are able of inhibiting some types of the mutated c-kit protein and one of them, imatinib mesylate, has shown a great efficacy in the treatment of gastro intestinal stromal tumors (GIST) which also involves the c-kit mutation. By analogy, treatment of patients with c-kit susceptible mutation might be treated with this molecule.

Inhibition of constitutively active forms of mutant kit by multitargeted indolinone tyrosine kinase inhibitors

Mutations in the proto-oncogene c-kit, including point mutations, deletions, or duplications in the negative regulatory juxtamembrane (JM) domain or point mutations in the catalytic domain, have been observed in human and canine cancers and often result in constitutive activation of Kit in the absence of ligand binding. To identify a receptor tyrosine kinase (RTK) inhibitor capable of blocking the function of mutant Kit, we evaluated 3 indolinones (SU11652, SU11654, and SU11655) that act as competitive inhibitors of adenosine triphosphate binding to several members of the split kinase family of RTKs, including VEGFR, FGFR, PDGFR, and Kit. Mast cell lines expressing either wild-type (WT) Kit, a point mutation in the JM domain, a tandem duplication in the JM domain, or a point mutation in the catalytic domain were used for these studies. All 3 indolinones inhibited phosphorylation of WT Kit in the presence of stem cell factor at concentrations as low as 0.01 microM. Autophosphorylation of both JM mutants was inhibited at 0.01 to 0.1 microM, resulting in cell cycle arrest within 24 hours, whereas autophosphorylation of the catalytic domain mutant was inhibited at 0.25 to 0.5 microM, resulting in cell death within 24 hours. poly(ADP-ribose) polymerase (PARP) cleavage was noted in all Kit mutant lines after indolinone treatment. In summary, SU11652, SU11654, and SU11655 are effective RTK inhibitors capable of disrupting the function of all forms of mutant Kit. Because the concentrations of drug necessary for receptor inhibition are readily achievable and nontoxic in vivo, these compounds may be useful in the treatment of spontaneous cancers expressing Kit mutations.

Mastocytosis: recent advances in defining the disease

Mastocytosis is a rare disease characterized by a primary pathological increase in mast cells in different tissues, which may present in a variety of clinical patterns. Major advances have been made in recent years in the understanding of the pathogenesis of mastocytosis. This review is aimed at familiarizing dermatologists with these recent findings, and at exploring their possible implications for the diagnosis and treatment of the condition. The heterogeneous clinical presentation of mastocytosis is detailed with respect to the type of skin lesions, age at onset, family history, organ systems involved, associated haematological disorders and prognosis. Recent genetic findings also indicate different pathogenetic forms of mastocytosis, as adult patients and those with associated haematological diseases usually express activating mutations of the stem cell factor receptor c-kit, whereas most cases of childhood-onset and familial mastocytosis seem to lack these mutations. Despite the presence of c-kit mutations, patients with cutaneous lesions generally have a good prognosis, even when there is involvement of other organs. Some patients, particularly those with childhood-onset disease, experience spontaneous remission, mostly by puberty. c-kit mutations do not explain the initial cause of mastocytosis, and their prognostic significance is as yet unclarified, as is the pathogenesis in patients without the mutations. Furthermore, these novel findings have as yet not resulted in a more effective treatment of the cause of the disease, so that counselling, prevention of exposure to mast cell secretory stimuli, and symptomatic treatment remain the mainstays of current patient management.

Treatment of systemic mast cell disorders

The heterogeneous nature of disease manifestations in mastocytosis requires the individualization of therapy to each patient's clinical presentation and prognosis. The mainstay of treatment for most categories of mastocytosis are H1 and H2 antihistamines with the addition of corticosteroids for more severe symptoms. This article presents a summary of treatment strategies for indolent and aggressive forms of mastocytosis along with a discussion of future therapeutic directions.

Gastrointestinal abnormalities and involvement in systemic mastocytosis

Recent studies have shown that involvement of the gastrointestinal tract is much more frequent than originally reported in patients with systemic mastocytosis. Seventy percent to 80% of patients with systemic mastocytosis are found to have gastrointestinal symptoms when a careful history is taken, and abnormalities in the gastrointestinal tract are frequently detected by endoscopic studies, functional studies of absorption, and barium studies. Because of the rarity of the disease, there are few prospective studies of gastrointestinal involvement, so the actual frequency of upper and lower gastrointestinal lesions is unknown. Furthermore, there have been no studies correlating endoscopic abnormalities of the lower gastrointestinal tract with the presence or absence of diarrhea, which is a frequent symptom (mean, 43% [range 14%-100%]). A review of gastric acid studies reveals that a proportion of patients develop gastric acid hypersecretion because of the hyperhistaminemia, which can result in ulcer disease that in turn can cause dyspeptic pain, small intestinal mucosal damage, and malabsorption. In some patients gastric acid hypersecretion in the range seen in Zollinger-Ellison syndrome can develop. A number of studies suggest that the prevalence of peptic ulcer disease has been underestimated in these patients and is certainly higher than the general population. The exact physiologic basis for the diarrhea or nondyspeptic abdominal pain remains largely unknown in these patients. Whereas some studies suggest small intestinal mucosal abnormalities are responsible for most cases of malabsorption not associated with gastric acid hypersecretion, this supposition also remains unproven. Hepatomegaly, portal hypertension, splenomegaly, and ascites occur frequently in patients with systemic mastocytosis, especially those with category II through IV disease. Whereas the histology of the liver and spleen and alterations in hepatic function studies have been well studied, the pathogenesis of each of these abnormalities has not been well studied, and almost all the information comes from a few well-studied case reports.