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As diverse pruritic cutaneous diseases respond to ultraviolet treatment, we have examined whether ultraviolet light is capable of inducing apoptosis in mast cells. Human mast cell line 1 (HMC1) derived from a patient with malignant mastocytosis and purified skin mast cells were irradiated with single doses of ultraviolet B or ultraviolet A1, or pretreated with 8-methoxypsoralen prior to ultraviolet A1 exposure. After 0 to 48 h of incubation, the percentage of apoptotic and dead cells was assessed. In HMC1 cells, morphologic features of apoptosis were further evaluated by electron microscopy. All ultraviolet treatment induced apoptosis of HMC1 cells in a time- and dose-dependent manner. Apoptosis was associated with activation of caspase-3, release of cytochrome C, cleavage of poly(ADP-ribose)-polymerase, and nuclear accumulation of p53. In contrast, resting skin mast cells were resistant to ultraviolet light induced apoptosis. After incubation with stem cell factor and interleukin-4 for 2 wk, however, slowly proliferating skin mast cells also underwent apoptosis in response to ultraviolet light. In conclusion, these data demonstrate that ultraviolet light directly affects mast cells, but mainly aims at the proliferating mast cells as found in mastocytosis and mast cell dependent pruritic diseases, where increased numbers are observed due to the recruitment mast cell precursors from the blood.

Resume La mastocytose systemique est une pathologie rare, parfois agressive, au diagnostic difficile. Nous rapportons l’observation d’une malade de 72 ans chez qui le diagnostic de mastocytose maligne a necessite la realisation de deux myelogrammes et trois biopsies osteomedullaires associees a des colorations specifiques. Malgre un traitement par interferon, un sarcome mastocytaire du sternum apparait un an apres le debut des symptomes suivi un an plus tard d’une leucemie aigue myeloblastique aboutissant rapidement au deces.

Objective To study clinicopathologic correlations and identify prognostically important variables in patients with systemic mast cell disease (SMCD) who have no associated hematologic disorders. Patients and Methods We identified 40 adult patients with SMCD without associated hematologic disorders. Clinical, laboratory, and bone marrow (BM) histologic findings at the time of referral were evaluated (November 1980-February 2001) for possible correlations with a history of aggressive systemic mastocytosis (retrospectively analyzed) as well as survival (prospectively analyzed). Results The median follow-up time from diagnosis was 108 months and from BM examination was 24 months. A history of aggressive systemic mastocytosis correlated significantly with increased BM mast cell (MC) content, unfavorable MC infiltration pattern, BM eosinophilia, and elevated serum alkaline phosphatase (SAP) level, but not with BM angiogenesis, reticulin fibrosis, or levels of MC mediators. Of these factors, increased BM MC content and elevated SAP level were also associated with shortened survival from time of referral. Conclusions This study suggests that the BM MC burden, BM eosinophilia, and SAP level are prognostically important in SMCD without associated hematologic disorders. In contrast, BM angiogenesis, reticulin fibrosis, and levels of MC mediators showed no prognostic relevance.

An increase in mast cell (MC) numbers in hemopoietic tissues may be associated with (a) primary neoplastic MC disease (mastocytosis); (b) non-mast cell lineage myelogenous disorders (myelodysplastic or myeloproliferative syndromes and myeloid leukemias); or (c) reactive, i.e. non-clonal states (MC hyperplasia and reactive mastocytosis). However, the histologic discrimination between hyperplastic states and neoplastic MC proliferative disorders is sometimes very difficult. MC hyperplasia is characterized by a diffuse increase in mature, round or spindle-shaped, metachromatic MC that are loosely scattered throughout the tissue and do not form dense focal infiltrates, even in states of marked hyperplasia. However, loosely scattered MC are also a prominent feature of many cases of myelodysplastic syndromes and acute leukemia involving the MC lineage. In contrast, the demonstration of dense, focal and/or diffuse MC infiltrates can be regarded as indicative of primary MC disease/mastocytosis. In addition to the highly diagnostic focal MC infiltrates, mastocytosis may also present with a predominantly diffuse or a mixed (diffuse and focal) infiltration pattern. The relatively rare diffuse pattern is usually dominated by atypical, often hypogranulated or even non-metachromatic MC and is associated with the aggressive or frankly malignant subtypes of systemic mastocytosis and MC leukemia. Although the demonstration of MC infiltrates in Giemsa-stained tissue sections is still very important for the diagnosis of mastocytosis, immunohistochemical techniques using antibodies against MC-associated antigens such as tryptase or c-kit (CD117) are essential for the identification of highly atypical, hypogranulated MC, especially in MC leukemia, and for the detection of small and even minute MC infiltrates.

Mastocytosis represents a mast cell proliferative disease that generally runs a benign clinical course, with spontaneous remissions mostly by puberty in childhood-onset disease, although rare forms, particularly in adult-onset disease, can be associated with (pre)malignant hematologic disorders and very rarely present as mast cell leukemia or malignant mastocytosis. Reasons for this divergent clinical behavior of childhood- versus adult-onset disease are unknown. Recently, two activating mutations in the intracellular domain of the proto-oncogene c-kit, which encodes a tyrosine kinase receptor for the mast cell growth factor stem cell factor, have been detected in the human leukemic mast cell line HMC-1. We have therefore studied lesional skin biopsies from patients with adult- and childhood-onset indolent mastocytosis for the presence of these codon 560 and 816 mutations. C-kit coding DNA sequences were amplified and analyzed by mutation-specific restriction analyses, and mutated polymerase chain reaction products were additionally cloned and sequenced. The codon 816 mutation was found in all six samples from adult patients, but not in any of the 11 specimens from children. In addition, the codon 560 mutation could be demonstrated for the first time in indolent mastocytosis, namely in two of four specimens from adult patients, but not in those from two children. These data thus provide a possible explanation for the divergent clinical behavior of adult- versus childhood-onset indolent mastocytosis, with the first being associated with an activating mutation, possibly as part of a neoplastic process, and the latter representing most likely a reactive process of an as yet unknown pathogenesis.

We present the case of a 40-year-old man with aggressive systemic mast cell disease. The patient had a predominant near-haploid clone in his bone marrow cells, detected by cytogenetic analysis performed at the time of diagnosis. The similarities between this case and a previously published case of near-haploidy in a patient with malignant mastocytosis suggest that near-haploidy may be a characteristic of aggressive systemic mast cell disease rather than an incidental finding.

Mastocytosis is a spectrum of disorders characterized by an aberrant proliferation of tissue mast cells. Although this disease process often affects the skin, it may involve multiple organs. The clinical disorder varies according to patient age, the clinical manifestations demonstrated, and the extent of the mast cell proliferative process. A myriad of clinical symptoms occur, and these may be localized to the organ system involved or may be systemic, depending on whether there is local or generalized mast cell mediator release. Diagnosis includes the demonstration of increased tissue mast cells in involved organs as well as increased levels of biochemical mediators. Patients with cutaneous involvement only have the best prognosis. Treatment is directed toward stabilizing mast cell mediator release and blocking the effects of those mediators generated.

Systemic mastocytosis is a rare and occasionally aggressive condition that raises major diagnostic challenges. We report a case in a 72-year-old patient in whom the diagnosis of malignant mastocytosis required two bone marrow smears and three bone marrow biopsies examined using specific staining techniques. Despite interferon therapy, a mast-cell sarcoma of the sternum developed 1 year after symptom onset, followed 1 year later by acute myeloblastic leukemia, which was rapidly fatal.

We describe a patient with fever and multiple osteolytic bone lesions accompanied by hypercalcemia, a duodenal ulcer, anemia, and thrombocytopenia. Bone marrow showed a dense infiltration by abnormal cells characterized by small basophil granula, erythrophagocytosis and nuclear atypia. These cells were positive for toluidine blue and partly for myeloperoxidase and chloroacetate esterase, expressed myeloid differentiation markers, and exhibited multiple numerical and structural chromosome aberrations. Molecular genetic analysis showed no breakpoint cluster region rearrangement. Electron microscopy demonstrated granula both of basophil and mast cell type. Concluding, in this patient an acute hematopoietic malignancy with many features of malignant mastocytosis but also with signs of a basophil differentiation. This is further support for a hematopoietic stem cell origin of human mast cells.

Mastocytosis is a disease characterized by an abnormal increase in mast cells. Manifestations of the disease are provoked in large part by the resultant increase in mast cell-derived mediators, which have a variety of local and systemic effects. Mastocytosis is variable in respect to the organ systems involved, clinical manifestations, and association with hematologic diseases. This has suggested the need for an improved classification scheme to allow assessment of prognosis and therapy. The heterogeneity of the disease patterns in mastocytosis strongly suggests that more than one biologic lesion may occur in the developmental sequence that leads to placement of mature mast cells in tissues.

We report the clinical and pathologic findings in one case of mast cell leukemia observed in a series of 60 patients with systemic mast cell disease. The leukemic variant of systemic mast cell disease is rapidly fatal (mean duration of survival, less than 6 months) in contrast to most nonleukemic cases, which follow an indolent clinical course. On the basis of our case and eight previously reported cases, mast cell leukemia is characterized by a substantial increase in atypical mast cells in the peripheral blood, diffuse infiltration with atypical mast cells in the bone marrow, a strong association with peptic ulcer disease, prominent constitutional symptoms, and hepatosplenomegaly. These cases should be distinguished from malignant mastocytosis without a substantial number of circulating atypical mast cells and also cases of acute nonlymphocytic leukemia that arise in the background of systemic mast cell disease.

Summary Mast cells (MC) are regular constituents of soft tissue and occur with varying frequency in nearly every organ. They derive from monocytic cells occuring in the adhering mononuclear fraction of the peripheral blood. Their subsequent evolution into mature MCs is primed by a MC generating lymphokine released by sensitized T-cells on restimulation by the antigen. MC granules contain preformed heparin histamine and eosinophil chemotactic factors. Other factors such as leukotriene B 4 can be produced by MCs following stimulation. This is the case during the initial phase of nonspecific inflammations, when MCs are stimulated by complement activation. In the immediate type hypersensitivity reaction giving rise to IgE, MC degranulation occurs independent from complement. In IgG and IgM mediated reactions, however, MC involvement is effected by complement consumption and C5 a generation. In delayed type hypersensitivity MCs increase locally. Their functional significance remains obscure. MC neoplasias are rare and generally confined to the dermis. Cutaneous mastocytoses are called benign mastocytoma when localized and urticaria pigmentosa when disseminated. Generalized mastocytosis involves extracutaneous tissue irrespective of skin involvement. Those associated with urticaria pigmentosa-like skin lesions, present at the onset of the disease, have a significantly higher survival rate than those lacking a primary skin involvement. The term urticaria pigmentosa should be reserved for cases of cutaneous mastocytosis without extracutaneous involvement. Cases of mastocytoses lacking primary skin lesions assume a malignant course and are additionally aggravated by high incidence of myeloproliferative disorders and MC leukemia. MC sarcoma is an extremely rare neoplasia of MCs which may also terminate as a MC leukemia.