Translocation (X;8)(q2?6;q21.3) in a case of systemic mastocytosis

Cytogenetic and molecular genetic abnormalities in systemic mastocytosis

Clonal cytogenetic abnormalities similar to those observed in other haematological neoplasms are demonstrable in a proportion of patients with systemic mastocytosis and in a smaller proportion of adults with urticaria pigmentosa without apparent systemic disease. These clonal abnormalities are not likely to represent the primary event in mast cell neoplasms. Although no recurrent cytogenetic abnormalities specific for mastocytosis have yet been recognized, the majority of cases display one of several mutations in c-KIT, the gene encoding the receptor for stem cell factor. That most commonly observed is the Asp816Val mutation, which permits proliferation independent of growth factors. c-KIT mutations may play a significant role in the biology of mast cell malignancies, although other mutations may be needed for a malignant phenotype.

Bone marrow involvement in cutaneous mastocytosis

BACKGROUND

Cutaneous mastocytosis is considered a relatively benign and indolent form of mast cell disease, which either ultimately regresses, remains stable or is only slowly progressive. Previously, it has been purported that no more than 60% of adult patients with cutaneous mastocytosis will have occult bone marrow involvement.

OBJECTIVES

To investigate the frequency of bone marrow involvement in patients with mastocytosis but without systemic symptoms.

METHODS

Bone marrow aspirate and trephine biopsy were performed in 13 consecutive patients with cutaneous mastocytosis attending our department.

RESULTS

All but one of these patients had evidence of bone marrow involvement. Bone marrow cytogenetic abnormalities have been found in patients with cutaneous mastocytosis: all our patients who were analysed showed a normal karyotype.

CONCLUSIONS

Bone marrow involvement is common in adults with cutaneous mastocytosis.

Cytogenetic studies in patients with mastocytosis

Chromosomal aberrations in hematopoietic cells are common in malignant hematological disorders and have also been reported in some patients with mastocytosis. In this study, 34 patients with either urticaria pigmentosa or systemic mastocytosis were investigated by cytogenetic analysis of bone marrow cells. A follow-up investigation was performed in 22 patients. Clones with chromosome abnormalities were found in 32% of the patients at the first examination and in 27% at the second examination; in total, 41% of the patients had an abnormal clone in at least one examination. No clinical correlation was found with regard to cytogenetic results, with the exception of four patients who had an associated hematological disease and poor prognosis. In the second examination, only 6 patients had an unchanged chromosome pattern, and 4 of the patients with an initial normal pattern had appearance of abnormal clones; however, in 7 patients, the initial abnormal cells disappeared. The abnormalities were, among others, deletions of chromosomes 5, 7, 11, and 20. The proportion of cells with structural or numerical chromosome changes was higher in comparison with reported control groups. The frequency and type of chromosome abnormalities in bone marrow cells from patients with mastocytosis was about the same as observed in other chronic myeloproliferative disorders and myelodysplastic syndromes, diseases which also developed in 4 of our patients. An association between malignant hematological disorders and mastocytosis have been suggested by us and others. The chromosome abnormalities maybe reflect a genetic instability of the hematopoietic cells in mastocytosis.

A near-haploid bone marrow karyotype in systemic mast cell disease: is it characteristic of the disease or an incidental finding?

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.