Paediatric mastocytosis

Decoding the intricacies of the mast cell compartment

Historically, understanding of the human mast cell (MC) compartment has lagged behind the appreciation of other cell lineages. MCs exist in vascularised tissues but do not under normal circumstances circulate in blood, and there has been no pharmacological agent identified that totally and selectively inhibits human MC function. There are no substantiated accounts of an apparently healthy individual who is severely lacking in MCs. Thus, some of the approaches employed to understand the function of a specific immune cell are not available to the MC biologist. The disease categories that have provided the greatest insight into MC biology have been monoclonal and IgE-mediated MC disorders. This has led to the categorisation of MC diseases as intrinsic or extrinsic to the MC compartment and to the recognition of the role of mediators in MC activation disorders. Mastocytosis as a clonal disorder not only impacts the MC compartment through changes intrinsic to the MC, but also by the effects of episodes of significant release of MC mediators. The availability of newer therapeutic approaches developed to treat monoclonal MC disorders offer insights into how to more selectively approach management of MC centric diseases.

Cutaneous Mastocytosis in Childhood-Update from the Literature

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

Mast cell activation in the context of elevated basal serum tryptase: genetics and presentations

PURPOSE OF REVIEW

To describe inherited and acquired genetic variants and clinical entities associated with increased basal serum tryptase (BST), distinguish these levels from those which acutely rise due to mast cell activation, and finally to characterize the association between chronically elevated basal serum tryptase and episodic mast cell activation.

RECENT FINDINGS

Hereditary alpha-tryptasemia is a commonly inherited genetic cause for basally elevated serum tryptase and explains elevated BST in many individuals who do not have evidence of clonal myeloid or mast cell disease. When clonal myeloid disease is present, BST may be elevated and can be a biomarker of a number of disparate disorders of the myeloid compartment. Elevated BST is most commonly caused by hereditary alpha tryptasemia but may also be indicative of clonal myeloid disease. Clinical reports suggest that elevated BST is associated with increased risk for more severe systemic allergic reactions to a number of eliciting agents and exposures. Additional studies are needed to determine the role that inherited or acquired genetic variants associated with elevated BST and clonal or non-clonal myeloid diseases may play in these reactions.

[Recurrent skin blisters for more than 7 months in a girl aged 15 months]

A girl, aged 15 months, attended the hospital due to recurrent skin erythema, blisters, and desquamation for more than 7 months. Giemsa staining and immunohistochemical staining showed mast cell infiltration and degranulation. Hematoxylin staining showed spinous layer edema and blister formation under the epidermis, with a large amount of serous fluid and a small number of inflammatory cells in the blister. Marked edema was observed in the dermis, with diffused mononuclear cell infiltration. The girl was diagnosed with mastocytosis. Mastocytosis should be considered for children with recurrent skin erythema and blisters.

Pediatric Expression of Mast Cell Activation Disorders

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

Diffuse Cutaneous Mastocytosis in a Child - a Case Report

Mastocytosis refers to a group of diseases characterized by a clonal proliferation and accumulation of mast cells in one or more tissues/organs with different clinical presentations. In children, limited cutaneous forms of mastocytosis are rather frequent, while systemic mastocytosis is rare. The diagnosis of cutaneous mastocytosis is based on clinical findings and histopathology. We present a patient who developed skin lesions at the age of 18 months. Clinical findings, confirmed by histopathology, were consistent with diffuse cutaneous mastocytosis. The follow-up period was 7 years. The treatment included oral antihistamines in combination with mast cell stabilizers, mild topical steroids and avoidance of friction. During the follow-up period, there were no signs of systemic involvement, and the quality of life was preserved, despite the large surface of affected skin. This case report should increase the awareness and knowledge of clinicians about this rare form of cutaneous mastocytosis in the pediatric population.

Mast cell activation syndromes

Mast cell activation is common and possibly necessary for maintenance of survival. Disordered mast cell activation occurs when mast cells are pathologically overproduced or if their activation is out of proportion to the perceived threat to homeostasis. Mast cell activation syndrome refers to a group of disorders with diverse causes presenting with episodic multisystem symptoms as the result of mast cell mediator release. Despite introduction of diagnostic criteria and some advances in treatment in the last decade, many areas of mast cell activation syndrome are in need of research. This article reviews our current knowledge about the various types of mast cell activation disorders, their treatment, and areas of uncertainty in need of future investigation.

Current approach to cutaneous mastocytosis in childhood

Mastocytosis is a heterogeneous disorder characterized by clonal proliferation and accumulation of mast cells in one of more organs which may lead to different clinical pictures. Pathological increase and activation of mast cells in various tissues can cause different clinical pictures. Cutaneous mastocytosis limited to the skin is the most typical clinical picture observed in children and systemic mastocytosis is very rare in the pediatric age group. The diagnosis of cutaneous mastocytosis is based on clinical findings, but is often delayed due to lack of clinical awareness of the disease and lack of its consideration in the differential diagnosis. This article focuses on the current diagnosis, management and treatment of cutaneous mastocytosis in children in order to increase awareness about this issue.

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

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

[Cutaneous mastocytosis: A case report]

INTRODUCTION

Mastocytosis represents a group of diseases characterised by an excesive accumulation of mastocytes in one or multiple tissues. It can affect only the skin, or have a systemic involvement. It has a low prevalence, and the prognosis is benign in children.

OBJECTIVE

To report a case of urticaria pigmentosa as a subtype of cutaneous mastocytosis, and present a literature review focused on clinical findings, diagnosis and initial basic management.

CLINICAL CASE

A child of six months of age presenting with multiple blemishes and light brown papules located on the trunk, arms and legs. The symptoms were compatible with urticaria pigmentosa, and was confirmed by biopsy. Tests to rule out systemic involvement were requested. The patient was treated with general measures, education, and antihistamines, with favourable results.

CONCLUSIONS

Cutaneous mastocytosis is a rare disease with a good prognosis. In childhood general measures and education are usually enough to obtain favourable results. Histamine H1 antagonists are the first line drug treatment.

Update on Mastocytosis (Part 1): Pathophysiology, Clinical Features, and Diagnosis

Mastocytosis is a term used to describe a heterogeneous group of disorders characterized by clonal proliferation of mast cells in various organs. The organ most often affected is the skin. Mastocytosis is a relatively rare disorder that affects both sexes equally. It can occur at any age, although it tends to appear in the first decade of life, or later, between the second and fifth decades. Our understanding of the pathophysiology of mastocytosis has improved greatly in recent years, with the discovery that somatic c-kit mutations and aberrant immunophenotypic features have an important role. The clinical manifestations of mastocytosis are diverse, and skin lesions are the key to diagnosis in most patients.

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

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

A clinicopathologic study of 24 cases of systemic mastocytosis involving the gastrointestinal tract and assessment of mucosal mast cell density in irritable bowel syndrome and asymptomatic patients

Counting mast cells in gastrointestinal (GI) mucosal biopsies is becoming an increasingly common practice. The primary reason for this exercise is to evaluate for possible involvement by systemic mastocytosis (SM). However, the features of mastocytosis in GI biopsies are not well described. In addition, recent studies have suggested that increased mast cells may be involved in the pathogenesis of some cases of diarrhea-predominant irritable bowel syndrome (IBS); the term "mastocytic enterocolitis" has been proposed for such cases. As the baseline mast cell density in colonic biopsies from normal patients has not been established in large cohorts, there is no widely accepted threshold for what constitutes increased mucosal mast cells. The aims of this study were (1) to determine the utility of GI biopsies for the diagnosis of SM, (2) to characterize the clinical, histologic, and immunohistochemical features of mastocytosis in the GI tract, (3) to determine mast cell density in normal colonic mucosa from a large cohort of asymptomatic patients, and (4) to compare these findings with those from patients with diarrhea-predominant IBS. Twenty-four patients with SM involving the GI tract, 100 asymptomatic patients, and 100 patients with IBS (the latter 2 groups with histologically normal colonic biopsies) were included. For the mastocytosis group, 107 biopsies (70 involved by mastocytosis; 67 mucosal, 3 liver) from 20 women and 4 men were evaluated (median age 59 y). The most commonly involved site was the colon (19 patients, 95%), followed by ileum (86%), duodenum (80%), and stomach (54%). In 16 cases (67%), the first diagnosis of SM was made on the basis of GI biopsies. Seventeen patients had documented cutaneous mastocytosis. Fifteen of 17 patients who underwent bone marrow biopsy had marrow involvement by SM. Eighteen patients had indolent disease, and 6 had aggressive disease (including all 3 with liver involvement). The most common GI symptom was diarrhea, followed by abdominal pain, nausea, weight loss, bloating, vomiting, or reflux. Liver disease presented with hepatomegaly and ascites. Endoscopic abnormalities (observed in 62%) included erythema, granularity, and nodules. Histologically, involved biopsies were characterized by infiltrates of ovoid to spindle-shaped mast cells in aggregates or sheets in the lamina propria, sometimes forming a confluent band underneath the surface epithelium; 25% of biopsies had only focal involvement (single aggregate). Prominent eosinophils were seen in 44% of involved colonic/ileal biopsies and 16% of duodenal biopsies. Mast cells were highlighted by diffuse membranous staining for KIT and CD25. In the nonmastocytosis groups, all biopsies contained singly dispersed mast cells with no aggregates. The mean highest mast cell counts (in a single high-power field) for asymptomatic patients and IBS patients were 26 (range, 11 to 55) and 30 (range, 13 to 59), respectively. In summary, GI (especially colonic) biopsies can establish a diagnosis of SM in patients with GI symptoms. GI involvement is usually subtle and is often associated with prominent eosinophils, which may obscure the mast cell infiltrate. KIT and CD25 are invaluable markers for the diagnosis. Mast cell density in colonic mucosa from asymptomatic patients is highly variable. Although patients with diarrhea-predominant IBS on average have mildly increased mast cells, the overlap in range with that of control patients is too great for this difference to be clinically useful. These findings argue against the utility of counting GI mucosal mast cell in patients with chronic diarrhea.

Primary mast cell disorders in children

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

Death from mast cell leukemia: a young patient with longstanding cutaneous mastocytosis evolving into fatal mast cell leukemia

   Mastocytosis is a broad term used for a group of disorders characterized by accumulation of mast cells in the skin with or without extracutaneous involvement. The clinical spectrum of the disease varies from only cutaneous lesions to highly aggressive systemic involvement such as mast cell leukemia. Mastocytosis can present from birth to adulthood. In children, mastocytosis is usually benign, and there is a good chance of spontaneous regression at puberty, unlike adult-onset disease, which is generally systemic and more severe. Moreover, individuals with systemic mastocytosis may be at risk of developing hematologic malignancies. We describe a girl who presented to us with a solitary mastocytoma at age 5 and later developed maculopapular cutaneous mastocytosis. At age 23, after an episode of anaphylactic shock, a bone marrow examination revealed mast cell leukemia. She ultimately died despite aggressive chemotherapy and bone marrow transplantation.

Mastocytosis in children and adults: clinical disease heterogeneity

Mastocytosis is a clonal disease of the hematopoietic stem cell. The condition consists of a heterogeneous group of disorders characterized by a pathological accumulation of mast cells in tissues including the skin, bone marrow, liver, spleen and the lymph nodes. Mastocytosis is a rare disease which occurs both in children and adults. Childhood onset mastocytosis is usually cutaneous and transient while in adults the condition commonly progresses to a systemic form. The heterogeneity of clinical presentation of mastocytosis is typically related to the tissue mast cell burden, symptoms due to the release of mast cell mediators, the type of skin lesions, the patient's age at the onset and associated haematological disorders. Therefore, a multidisciplinary approach is recommended. The present article provides an overview of clinical symptoms, diagnostic criteria and treatment of mastocytosis to facilitate the diagnosis and management of mastocytosis patients in clinical practice.

[Bullous mastocytosis in infancy: a rare presentation]

Mastocytosis is a rare condition related to an abnormal proliferation of mast cells and their accumulation in tissues. Cutaneous mastocytosis is the most common form and mainly affects newborns and infants. The symptoms are caused by the release of mediators contained in mast cells, including histamine. Mastocytosis may be associated with a mutation in the gene encoding the c-kit receptor. Clinically, there are different dermatological findings, which combine acute cutaneous, digestive, or even hemodynamic manifestations in varying degrees. The diagnosis is confirmed by the histological study of a skin sample. We report here the case of a 4-month-old infant suffering from diffuse cutaneous bullous mastocytosis, a very rare variety of mastocytosis. This infant had an erosive and bullous manifestation of dermatosis, initially confused with impetigo. The proliferation of bullous lesions led to her hospitalization. Codeine intake for pain was responsible for a large and extensive bullous reaction associated with anaphylactic shock. This context of bullous spread occurring after taking codeine led to the suspicion of bullous diffuse cutaneous mastocytosis, a diagnosis that was confirmed histologically. This observation demonstrates the difficulty of mastocytosis diagnosis, mostly due to its rarity, especially in its diffuse bullous forms. The rapid deterioration of this patient, after the codeine prescription, emphasizes the importance of the eviction of histamine-releaser compounds in the management of this disease.

Refractory symptoms successfully treated with leukotriene inhibition in a child with systemic mastocytosis

Montelukast was effective in treating refractory abdominal and urinary symptoms in a child with systemic mastocytosis.

Anaphylaxis and mast cell disease: what is the risk?

Mastocytosis is a proliferative disorder of the hematopoietic mast cell progenitor that results from expansion of a clone carrying the D816V c-kit mutation. Based on the dramatic increase in incidence of anaphylaxis in patients with mastocytosis, recent studies analyzed the presence of clonal mast cell markers, including D816V c-kit mutation, in patients with recurrent IgE- and non-IgE-mediated anaphylaxis. These studies demonstrated the presence of an aberrant mast cell clone in a significant proportion of patients with unexplained anaphylaxis, or anaphylaxis due to hymenoptera venom. Clonal mast cell disease should be suspected in particular in patients presenting with profound cardiovascular manifestations such as hypotension and syncope in the absence of urticaria.

Nodular Mastocytosis of the Vulva and Coexisting Urticaria Pigmentosa / Nodularna Mastocitoza vulve udružena sa urtikarijom pigmentozom

Nodular forms of mastocytosis are rather rare skin diseases, especially when localized on the vulva. A 9-year-old girl presented with urticaria pigmentosa type lesions since her 4th year, associated with several solitary or confluent vulvar nodules, varying in size from a pea to a walnut, and mild systemic symptoms. Diagnosis of mastocytosis was confirmed by histology, and apart from splenomegaly, no signs of systemic spread or associated hematologic disorders were detected. Therapeutic response of nodular lesions was rather poor, and further follow up is necessary.

Anesthesia in children with mastocytosis--a case based review

INTRODUCTION

Mastocytosis is a rare heterogeneous disease of bone marrow origin which arises as a consequence of abnormal growth and/or accumulation of clonal mast cells in one or more organs. Sixty-five percent of patients with mastocytosis are children in whom it usually regresses around puberty. Adult patients with mastocytosis have been identified as at high risk of widespread mast cell degranulation in the perioperative period, this finding has not been reported in pediatric patients. This information has been repeated in mastocytosis websites where it has the potential to cause disproportionate alarm in parents.

METHODS

We considered our experience of six children with mastocytosis together with a review of the literature to examine other reports of anesthesia in children with mastocytosis. Our literature search found 57 general anesthetics in 39 children with mastocytosis. In addition, we searched for information about current consensus in diagnosis, classification and treatment of mastocytosis and in vitro and in vivo studies looking at mast cell behavior in response to drugs commonly used during anesthesia.

DISCUSSION

The literature search revealed that general anesthesia has precipitated life threatening complications in adult patients with systemic mastocytosis (SM) but no such complications have been described in children with mastocytosis. Our own experience with children with mastocytosis is of uneventful anesthesia. Advances in the understanding of the genetic basis of mastocytosis suggest that pediatric cutaneous mastocytosis (CM) and SM are different entities. SM in children is extremely rare and is associated with elevated baseline serum tryptase. There are few reports of anesthesia in this group.

CONCLUSION

The risks for most pediatric patients are overstated by mastocytosis websites. Most pediatric patients with CM do not appear to be at risk of widespread mast cell degranulation during anesthesia but because of the small number of cases reported, the risk cannot be ascertained with confidence. Children with SM and a high baseline serum tryptase (marker of mast cell burden) may merit extra precautions but experience in this subgroup is even more limited. Drugs which cause minimal histamine release can be selected from the range of drugs available in most pediatric centers without compromise to technique.

Mastocytosis and allergy

PURPOSE OF REVIEW

To illustrate features of allergy in mastocytosis.

RECENT FINDINGS

The rates of atopy in patients with mastocytosis have generally been found to be similar to those of the normal population, although the incidence of anaphylaxis is much higher in mastocytosis. Introduction of objective pathologic criteria by the WHO for the diagnosis of mastocytosis has greatly facilitated the workup of patients with suspected mastocytosis, and has led to identification of mast cell disease in a subset of patients with anaphylaxis. There is increasing evidence that an activating c-kit mutation (D816V) exists in a subset of patients with recurrent mast cell activation symptoms who have normal-appearing bone marrow biopsies in routine evaluations without skin lesions. The genetic deficiency of alpha tryptase has not been found to influence serum tryptase levels in patients with mastocytosis.

SUMMARY

Pathologic mast cell activation is a key finding in both allergic diseases and mastocytosis, albeit caused by entirely different mechanisms. Mastocytosis should be suspected in patients with recurrent anaphylaxis, who present with syncopal or near-syncopal episodes without associated hives or angioedema.

Mastocytosis: advances in diagnosis and treatment

Mastocytosis is characterized by pathologic mast cell accumulation and activation in tissues. Establishment of objective histopathologic and molecular criteria for diagnosis of mastocytosis has allowed sensitive detection of mast cells with aberrant features in patients presenting with suspected mast cell activation symptoms. Frequent detection of the D816V c-kit tyrosine kinase mutation in mastocytosis has led to evaluation of small-molecular-weight tyrosine kinase inhibitors as mast cell cytoreductive agents. In vitro experiments, however, showed that mast cells carrying the D816V c-kit mutation were resistant to the prototypical tyrosine kinase inhibitor imatinib. Efficacy of newer generation tyrosine inhibitors in mast cell disease is currently being evaluated.

Urticaria pigmentosa and mastocytosis: the role of immunophenotyping in diagnosis and determining response to treatment

Recent advances in our understanding of mast cell biology and disease resulted in identification of important differences in expression of mast cell surface antigens in normal and neoplastic mast cells. Most notably, detection of aberrant expression of CD25 and CD2 on the surface of neoplastic mast cells but not on their normal counterparts leads to the inclusion of this immunophenotypic abnormality in the World Health Organization's diagnostic criteria for systemic mastocytosis. Aberrant mast cell surface marker expression can be detected in the bone marrow aspirate by flow cytometry, even in patients with limited disease that lacks histopathologically detectable aggregates of mast cells in bone marrow biopsy sections. Flow cytometric analysis of bone marrow mast cells is therefore a sensitive method of diagnosis of mast cell disease and is expected to find increasing use in determining response to emerging mast cell cytoreductive therapies.

Tryptase detection in bone-marrow blood: a new diagnostic tool in systemic mastocytosis

BACKGROUND

The condition mastocytosis includes a heterogenous group of disorders that are characterized by abnormal growth and accumulation of mast cells. The detection of serum tryptase, an essential mast cell enzyme, is a widely used tool in the diagnosis of mastocytosis. The diagnosis of systemic mastocytosis is substantially based on the histologic examination of bone-marrow biopsy specimens.

OBJECTIVE

We hypothesized that the detection of tryptase in bone-marrow blood might provide additional, more sensitive information on the bone-marrow involvement of patients with mastocytosis.

METHODS

Serum tryptase was monitored in patients with cutaneous symptoms (n = 17), patients with extracutaneous symptoms (n = 16), and healthy control subjects (n = 359). Bone-marrow biopsy specimens of patients with systemic mastocytosis (n = 7) and control subjects (n = 7) were investigated histologically and bone-marrow blood of these individuals was analyzed on the tryptase levels.

RESULTS

We could detect for the first time significantly elevated tryptase levels in bone-marrow blood of patients with systemic mastocytosis. Secondarily we could present a clear correlation between the level of serum tryptase and the clinical symptoms of mastocytosis.

LIMITATIONS

With the present study, we establish a new diagnostic tool for systemic mastocytosis. Unfortunately, we can only present a limited number of cases, since systemic mastocytosis is a rare disease involving few patients.

CONCLUSION

Our results indicate that the measurement of tryptase in bone-marrow blood is a new, sensitive marker of the mast cell burden in bone marrow of patients with systemic mastocytosis.

Molecular diagnosis of mast cell disorders: a paper from the 2005 William Beaumont Hospital Symposium on Molecular Pathology

Mastocytosis is a disease characterized by pathological mast cell accumulation and activation in tissues. Most patients with mastocytosis exhibit the D816V point mutation in the tyrosine kinase domain of the transmembrane receptor protein Kit, leading to its constitutive activation in bone marrow or lesional skin tissue. Detection of a codon 816 c-kit mutation is included as a minor diagnostic criterion in the World Health Organization's diagnostic criteria for systemic mastocytosis. Determining mutational status of the c-kit gene also has pharmacogenomic implications in patients considered for investigational mast cell cytoreductive therapies. This article reviews diagnostic and therapeutic implications of c-kit mutations as well as other less common molecular abnormalities observed in mast cell disease.

Clonality and molecular pathogenesis of mastocytosis

Mast cell is a hematopoietic lineage dependent on Kit signaling for growth, differentiation, and survival. Mast cells are found in excessive numbers in tissues in a heterogeneous group of disorders collectively known as mastocytosis. Last decade has witnessed important advancements in our understanding of the molecular pathology of mastocytosis. First, systemic mastocytosis has been found to be associated with activating codon 816 mutations of the c-kit gene. Second, this mutation was used as a tracking marker to elucidate the clonal nature of mastocytosis. These findings have resulted in consideration of systemic mastocytosis as a clonal neoplastic disorder of a hematopoietic progenitor cell. Improved knowledge of the mechanisms causing pathological mast cell growth will lead to the discovery of novel treatment options including drugs targeting the mutated Kit protein.

Systemic mastocytosis

Systemic mastocytosis is a clonal disorder of the mast cell and its progenitor. The symptoms of systemic mastocytosis are due to the pathologic accumulation and activation of mast cells in various tissues such as bone marrow, skin, gastrointestinal tract, liver, and spleen. Recent studies revealed striking differences between the molecular and cellular biology of mast cells in patients with mastocytosis and those of healthy individuals. These findings are being used in formulating diagnostic criteria as well as designing novel treatment approaches to the disease.