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

Current concepts on diagnosis and treatment of mastocytosis

Mastocytosis is a heterogeneous group of disorders characterized by a clonal proliferation and accumulation of mast cells in one or more organ, primarily in the skin and bone marrow. The clinical spectrum of the disease varies from relatively benign forms with isolated skin lesions to very aggressive variants with extensive systemic involvement and poor prognosis. The growth and proliferation of clonal mast cells is caused by an activating mutation of the tyrosine kinase receptor Kit for Stem Cell Factor, the main growth factor for mast cells. Clinical symptoms are related to mast-cell mediator release, to the tissue mast cell infiltration or both. The degree of infiltration and cell activation determines the highly variable clinical and morphological features. Current treatment of mastocytosis includes symptomatic, antimediator drugs and cytoreductive targeted therapies.

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 mast cell activation disease: the role of molecular genetic alterations in pathogenesis, heritability and diagnostics

Despite increasing understanding of its pathophysiology, the aetiology of systemic mast cell activation disease (MCAD) remains largely unknown. Research has shown that somatic mutations in kinases are necessary for the establishment of a clonal mast cell population, in particular mutations in the tyrosine kinase Kit and in enzymes and receptors with crucial involvement in the regulation of mast cell activity. However, other, as yet undetermined, abnormalities are necessary for the manifestation of clinical disease. The present article reviews molecular genetic research into the identification of disease-associated genes and their mutational alterations. The authors also present novel data on familial systemic MCAD and review the associated literature. Finally, the importance of understanding the molecular basis of inherited mutations in terms of diagnostics and therapy is emphasized.

Childhood mastocytosis

PURPOSE OF REVIEW

Important advances have been achieved in recent years in adult mastocytosis. However, our knowledge about childhood mastocytosis is limited because invasive tests are not routinely performed in children. We ignore the frequency of systemic involvement in childhood mastocytosis, its outcome, and which are the main clinical and laboratory parameters associated with persistence into adult mastocytosis and its severity.

RECENT FINDINGS

Childhood mastocytosis is a clonal mast cell disease, with different activating mutations in the KIT gene discovered in most patients. Serum tryptase is the best marker for mast cell burden in children, and, at baseline, correlates well with the severity of symptoms in childhood mastocytosis. Systemic mastocytosis definitely may occur in children, but bone marrow studies to demonstrate a systemic involvement are not routinely performed nor recommended; it can be estimated that around 30% of children may have bone marrow involvement as demonstrated by showing aggregates of mast cells or by flow cytometry of mast cells expressing the aberrant CD25 marker.

SUMMARY

A new and improved classification of childhood mastocytosis is needed, and should be based on the correlation of clinical manifestations, morphology of mast cells in the skin, and the predicted outcome of the disease. The current classifications of childhood mastocytosis do not address any of these important issues.

[Childhood-onset mastocytosis]

Mastocytoses are a group of rare diseases characterized, in most cases, by a benign proliferation and accumulation of mast cells in different tissues. In children, mastocytosis affects usually exclusively the skin and differs in many aspects from adult-onset mastocytosis. Except for diffuse cutaneous mastocytosis, which is an uncommon subtype of childhood-onset mastocytosis, involvement of the bone marrow or additional extracutaneous organs is rarely seen in children. The prognosis of childhood-onset mastocytosis is usually very good. Compared to adult patients who most commonly experience chronic-stable or slowly progressive disease, mastocytosis in children is mostly transient and self-limiting. In this review, we present and discuss the subtypes of childhood-onset mastocytosis, recent advances in the understanding of their pathogenesis as well as similarities and differences between adult- and childhood-onset mastocytosis.

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.

Myelomastocytic Leukemia With t(8;21) in a 3-year-old Child

Here we report a 3-year-old boy with myelomastocytic leukemia. The patient presented with fatigue and right eye proptosis. Bone marrow revealed acute myeloid leukemia with t(8;21) and trisomy 8. Induction therapy produced marked reduction in marrow myeloblasts with the emergence of 13% atypical mast cells. These cells were subsequently identified in retrospect in the diagnostic marrow consistent with myelomastocytic leukemia. His clinical course was notable for the difficulty in the eradication of the leukemic process and resembled that of adults with systemic mastocytosis with associated hematologic non-mast cell lineage disease. To the best of our knowledge, this is the youngest individual reported. The implications of mast cell lineage involvement in acute myeloid leukemia are reviewed.

Update on diagnosis and treatment of mastocytosis

Mastocytosis is a disorder characterized by increased numbers of mast cells in tissues. Recent clinical observations highlight the association of mastocytosis with an increased risk of anaphylaxis and underline the diversity of this disease. At the molecular level, recent studies have attempted to unravel specific gene expression profiles for activating c-kit mutations in the etiology of mastocytosis. The diagnosis may be facilitated by surrogate markers and detection of aberrant immunophenotypic surface markers. New therapeutic strategies are in development based on intracellular signal pathways, or on application of topical treatments, as are novel forms of cytoreductive therapy, including tyrosine kinase inhibitors.

Systemic mastocytosis in a child with t(8;21) acute myeloid leukemia

Mastocytosis is primarily limited to the cutaneous variant in pediatric patients. Systemic mastocytosis (SM) has been associated with t(8;21) acute myeloid leukemia (AML) in adults. We provide the first report of a child with t(8;21) AML, diagnosed with asymptomatic SM following four cycles of chemotherapy. Unlike most adults with SM/AML, she was not found to have a c-KIT (D816V) mutation. SM persisted in the bone marrow after completion of chemotherapy, and her AML relapsed 9 months off-treatment. Although she achieved a second remission, mastocytosis persists in the marrow. Pediatric patients with t(8;21) AML/SM may represent a high-risk group despite favorable cytogenetics.

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.

[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.