Bone marrow involvement in cutaneous mastocytosis

Clinical observations in cutan mastocytosis

Introduction: Mastocytosis is a clonal mast cell proliferative disease, devided into cutaneous and systemic forms. The characteristic symptoms are caused by neoplastic mast cell infiltrations in different organs and/or the release of mediators. Aim: The aim of the authors was to summarize their clinical observations in patients with mastocytosis. Method: 22 adult patients diagnosed consecutively with mastocytosis were enrolled in the study. Skin and bone marrow biopsies were taken to establish the diagnosis and perform c-KIT mutation (D816V) analysis. Results: One of the 22 patients had teleangiectasia macularis eruptiva perstans, while 20/22 patients had urticaria pigmentosa. All patients had cutaneous lesions. In 12 patients iliac crest biopsy was performed and 9 of them had bone marrow involvement, classified as indolent systemic mastocytosis. The c-kit mutation D816V was found in one subject both in skin and bone marrow samples. The patients were treated with antihistamine, PUVA, interferon-α or imatinib. Conclusions: The authors draw attention to this rare disease in order to help recognition of relevant signs and symptoms and establish an early diagnosis. Orv. Hetil., 2013, 154, 1469–1475.

PTEN deficiency in mast cells causes a mastocytosis-like proliferative disease that heightens allergic responses and vascular permeability

Kit regulation of mast cell proliferation and differentiation has been intimately linked to the activation of phosphatidylinositol 3-OH kinase (PI3K). The activating D816V mutation of Kit, seen in the majority of mastocytosis patients, causes a robust activation of PI3K signals. However, whether increased PI3K signaling in mast cells is a key element for their in vivo hyperplasia remains unknown. Here we report that dysregulation of PI3K signaling in mice by deletion of the phosphatase and tensin homolog (Pten) gene (which regulates the levels of the PI3K product, phosphatidylinositol 3,4,5-trisphosphate) caused mast cell hyperplasia and increased numbers in various organs. Selective deletion of Pten in the mast cell compartment revealed that the hyperplasia was intrinsic to the mast cell. Enhanced STAT5 phosphorylation and increased expression of survival factors, such as Bcl-XL, were observed in PTEN-deficient mast cells, and these were further enhanced by stem cell factor stimulation. Mice carrying PTEN-deficient mast cells also showed increased hypersensitivity as well as increased vascular permeability. Thus, Pten deletion in the mast cell compartment results in a mast cell proliferative phenotype in mice, demonstrating that dysregulation of PI3K signals is vital to the observed mast cell hyperplasia.

Phenotypic and genotypic characteristics of mastocytosis according to the age of onset

Adult's mastocytosis is usually associated with persistent systemic involvement and c-kit 816 mutation, while pediatrics disease is mostly limited to the skin and often resolves spontaneously. We prospectively included 142 adult patients with histologically proven mastocytosis. We compared phenotypic and genotypic features of adults patients whose disease started during childhood (Group 1, n = 28) with those of patients whose disease started at adult's age (Group 2, n = 114). Genotypic analysis was performed on skin biopsy by sequencing of c-kit exons 17 and 8 to 13. According to WHO classification, the percentage of systemic disease was similar (75 vs. 73%) in 2 groups. C-kit 816 mutation was found in 42% and 77% of patients in groups 1 and 2, respectively (p<0.001). 816 c-kit mutation was associated with systemic mastocytosis in group 2 (87% of patients with systemic mastocytosis vs. 45% with cutaneous mastocytosis, p = 0.0001). Other c-kit activating mutations were found in 23% of patients with mastocytosis' onset before the age of 5, 0% between 6 and 15 years and 2% at adults' age (p<0.001). In conclusion, pathogenesis of mastocytosis significantly differs according to the age of disease's onset. Our data may have major therapeutic relevance when considering c-kit-targeted therapy.

C-kit Asp-816-Val mutation analysis in patients with mastocytosis

BACKGROUND

Mastocytosis is a heterogeneous group of disorders characterized by abnormal accumulation of mast cells.

OBJECTIVE

Skin biopsies from 24 patients (23 with proven mastocytosis) were screened for the presence of the c-kit Asp-816-Val mutation.

METHODS

In frozen biopsies, RNA was isolated, cDNA synthesis and PCR, the expected PCR product of 346 bp was obtained from 23 patients.

RESULTS

In patients with urticaria pigmentosa, the mutation was detected in 38% of the adults and 25% of the children. With regard to the clinical presentation of the disease, no difference was found between adult patients with and without the mutation, as detected with our assay. One out of the 2 children with the mutation had an atypical presentation of the disease.

CONCLUSION

the mutation could not be detected in all the patients, probably due to lack of sensitivity of the methods.

Urticaria pigmentosa

Urticaria pigmentosa (UP), resulting from the accumulation of excessive numbers of mast cells in the skin, is the most common form of cutaneous mastocytosis. Observations highlight the diversity of this disease. Clonal expansion of early hematopoietic progenitor cells carrying activating mutations in KIT seems to be the basis of adult-onset UP. New pathogenetic findings are leading to the development of new diagnostic surrogate markers of disease and therapeutic approaches targeting neoplastic mast cells. Promising strategies may arise from an increased understanding about the cause of mastocytosis and the signaling pathways initiated by kit activation.

Clinical, genetic, and therapeutic insights into systemic mast cell disease

PURPOSE OF REVIEW

Mast cell disease is markedly heterogeneous in its underlying molecular pathogenesis, clinical presentation, natural history, and specific treatment. Skin-only disease (cutaneous mastocytosis) is infrequent in adults and systemic mastocytosis may be broadly classified as an indolent or aggressive variant based on the absence or presence of impaired organ function. Urticaria pigmentosa and mast cell mediator release symptoms can occur in all categories of mast cell disease and may not be prognostically detrimental. The purpose of this review is to summarize current concepts and recent advances in the pathogenesis and treatment of adult mast cell disease.

RECENT FINDINGS

A series of laboratory investigations has revealed that mast cell disease is a clonal stem cell disorder, and at least two genes (c-kit and PDGFRA) with pathogenetically relevant mutations have been identified. FIP1L1-PDGFRA+ mast cell disease responds completely to imatinib mesylate. Both Asp816Val c-kit+ and molecularly undefined cases have been shown to respond to 2-chlorodeoxyadenosine therapy after failing treatment with interferon-alpha.

SUMMARY

A partial molecular classification of mast cell disease is now possible; Asp816Val c-kit+, FIP1L1-PDGFRA+, and molecularly undefined cases. Such molecular classification is therapeutically relevant.

Mastocytosis. Curr Opin Allergy Clin Immunol. 2001;1:449-454. [PMID: 11964726 DOI: 10.1097/00130832-200110000-00011]

Mastocytosis is defined by a pathological increase in mast cell numbers in tissues. Recent clinical observations on rare manifestations highlight the diversity of this disease. The diagnosis is now aided by new surrogate markers. At the molecular level, recent studies have reinforced the role of activating mutations in KIT in the etiology of mastocytosis. These findings provide a conceptual basis for the development for new therapeutic strategies.