A novel translocation t(3;22)(q21;q11) involving 3q21 in myelodysplastic syndrome-derived overt leukemia with thrombocytosis

Megakaryocyte development and platelet production

Megakaryocytopoiesis involves the commitment of haematopoietic stem cells, and the proliferation, maturation and terminal differentiation of the megakaryocytic progenitors. Circulating levels of thrombopoietin (TPO), the primary growth-factor for the megakaryocyte (MK) lineage, induce concentration-dependent proliferation and maturation of MK progenitors by binding to the c-Mpl receptor and signalling induction. Decreased platelet turnover rates results in increased concentration of free TPO, enabling the compensatory response of marrow MKs to increased platelet production. C-Mpl activity is orchestrated by a complex cascade of signalling molecules that induces the action of specific transcription factors to drive MK proliferation and maturation. Mature MKs form proplatelet projections that are fragmented into circulating particles. Newly developed thrombopoietic agents operating via c-Mpl receptor may prove useful in supporting platelet production in thrombocytopenic state. Herein, we review the regulation of megakaryocytopoiesis and platelet production in normal and disease state, and the new approaches to thrombopoietic therapy.

An indolent case of T-prolymphocytic leukemia with t(3;22)(q21;q11.2) and elevated serum beta2-microglobulin

We report a novel case of T-prolymphocytic leukemia, small cell variant, associated with complex cytogenetic findings including t(3;22)(q21;11.2) and elevated serum beta2-microglobulin. The diagnosis is based on morphologic, immunophenotypic, cytogenetic, and molecular analysis of peripheral blood and bone marrow. In contrast to most reported cases of T-prolymphocytic leukemia, this patient did not present with lymphadenopathy or organomegaly. Moreover, only a moderate leukocytosis (25.3 x 10(3)/microL) was evident at presentation. In the absence of any specific treatment, the patient is doing well, with a stable white blood cell count 12 months following presentation. Further investigation may be warranted to determine whether the unusual cytogenetic findings and elevated serum beta2-microglobulin are associated with the indolent clinical course in this patient.

A retrospective analysis of myelodysplastic syndromes with thrombocytosis: reclassification of the cases by WHO proposals

Myelodysplastic syndromes (MDS) show occasionally thrombocytosis, common feature of myeloproliferative diseases (MPD), with the overlapping of both disorders. Classically, thrombocytosis has been associated with some MDS subtypes: refractory anaemia with ringed sideroblasts (RARS), 5q- syndrome and those MDS with 3q chromosome rearrangements. The recent WHO classification recognises an unclassifiable MDS/MPD category including some of these disorders. Our aim is to determine the frequency of presentation, subtype classification and chromosome abnormalities of MDS with thrombocytosis diagnosed in our institution. Between 1990 and 2003 we studied 317 SMD patients according to FAB and WHO revised classifications and identified 22 cases presenting thrombocytosis associated with dysplasia, that are analysed in this article.

Dysplastic changes in the peripheral blood of children with microdeletion 22q11.2

Myelodysplasia refers to abnormal morphology of the bone marrow and/or peripheral blood. This condition is frequently due to myelodysplastic syndrome; however, myelodysplasia is caused by a variety of factors and is not always a sign of pre-malignant disease. We observed myelodysplastic changes in peripheral blood smears and bone marrow specimens from a patient who had chromosomal microdeletion 22q11.2 (del22q11.2). We then investigated such changes in several other patients who were newly diagnosed with del22q11.2 (n = 5 total, including the index case) and compared the findings to those in four sets of controls without this chromosomal abnormality. Specifically, the controls were children with conotruncal heart defects (n = 3); otherwise healthy children with bacterial (n = 4) or viral infection (n = 4); and healthy children (n = 4). The myelodysplasia scores in the myeloid cells and eosinophils of the children with del22q11 were higher than those in all four of the control groups. Myelodysplastic changes in the peripheral blood of children with del22q11.2 have not been reported previously. We believe that certain gene(s) in the deleted region may be responsible for the myelodysplastic changes that we observed in our patients with this chromosomal abnormality.

Acute myelogenous leukemia associated with extreme symptomatic thrombocytosis and chromosome 3q translocation: case report and review of literature

Acute leukemias with thrombocytosis have been recently linked with structural abnormalities of the short arm of chromosome 3. A 46-year-old man with a 2-month history of recurrent transient ischemic attacks and abdominal pain developed an ischemic left foot and a gangrenous toe as his initial symptoms. Platelet count was 3.5 x 10(6)/microL, and despite plateletpheresis, the patient required left-leg amputation. Pathologic examination was remarkable for arterial thrombosis in the absence of atherosclerotic lesions. A diagnosis of acute myeloid leukemia with a novel translocation between chromosomes 3q21, 16, and 7 was made. Induction therapy was unsuccessful, and the patient died of overwhelming sepsis within 5 weeks of diagnosis. The striking features of this case were extreme symptomatic thrombocytosis, peripheral gangrene without atherosclerosis, and a novel three-way chromosomal translocation involving chromosome 3q21.

Thalidomide paradoxical effect on concomitant multiple myeloma and myelodysplasia

We present five cases of concomitant relapsed multiple myeloma and therapy related myelodysplasia (t-MDS). After treatment with thalidomide marked anti-myeloma activity was observed, but it was associated with rapid progression of the MDS clone to acute myeloid leukemia (AML). This paradoxical effect of thalidomide is concerning because there is increasing use of thalidomide in relapsed, heavily treated multiple myeloma patients who already have a higher propensity to develop MDS. The leukemic transformation in our cases most probably reflects the natural progression of MDS, though it clearly demonstrates that thalidomide is ineffective in controlling blast proliferation in t-MDS. More concerning, however, is the possibility that thalidomide, while suppressing the myeloma clone, eliminates inhibitory signals and subsequently stimulates the proliferation of the leukemic clone. The use of thalidomide should be carefully assessed in relapsed multiple myeloma patients with clinical and cytogenetic evidence of t-MDS.

Myelodysplastic syndrome: review of the cytogenetic and molecular data

Myelodysplastic syndrome (MDS) is a monoclonal disorder of the pluripotent stem cell that frequently evolves into acute leukemia. MDS is characterized by trilineage dysplasia and by ineffective hematopoiesis. The etiology of MDS is poorly understood. However, the frequent association of chromosomal abnormalities (deletions, inversions, translocations, trisomies and monosomies) with MDS suggests that an oncogene, or a tumor suppressor gene might be involved in the pathogenesis and evolution of this disorder. This review summarizes the clinical, laboratory, chromosomal and prognostic findings of some of the cytogenetic abnormalities such as; 20q deletion, chromosome 5, 7 and 3 abnormalities, 17p-syndrome, trisomy 8, and loss of Y chromosome. In addition, this review goes into the discussion of the most recent development in the field of molecular biology to understand some of the mechanisms resulting in the development and progression of MDS.