Summary

The myelodysplastic syndromes are heterogeneous clonal stem cell disorders characterized by dysplastic pathological features, clinical peripheral cytopenias, and a tendency to progress to AML.

The pathogenesis of MDS includes clonal gene function alterations due to single-gene alteration, chromosomal abnormalities or epigenetic phenomenon. Apoptosis can explain the paradoxical observation of peripheral cytopenias and normo- or hypercellular bone marrow. Different mechanisms, such as abnormal cytokines production and intrinsic clonal susceptibility lead to excessive apoptosis. Alterations in the a

Pseudo Pelger Huet Cell

Figure 38.1 Bone marrow: (a) megaloblastoid erythroid precursor, pseudo-Pelger-Huet neutrophils (bilobed and hypogran-ular), and a myeloblast with Auer rods; (b) dysplastic erythroid precursors, bi-nucleated erythroid precursor, and a myeloblast; (c) mononuclear and micromegakaryocytes; (d) Prussian blue stain of the bone marrow showing a ring sideroblast d

Figure 38.1 Bone marrow: (a) megaloblastoid erythroid precursor, pseudo-Pelger-Huet neutrophils (bilobed and hypogran-ular), and a myeloblast with Auer rods; (b) dysplastic erythroid precursors, bi-nucleated erythroid precursor, and a myeloblast; (c) mononuclear and micromegakaryocytes; (d) Prussian blue stain of the bone marrow showing a ring sideroblast immune system and bone marrow microenvironment clearly contribute to the development of MDS.

Pathologically, dysplasia is the hallmark of the disease. A careful pathological exam of the peripheral blood and bone marrow aspirate, and biopsy is necessary for diagnosis and better classification. MDS remains a diagnosis of exclusion. Cytogenetic testing using conventional analysis as well as molecular methods, such as fluorescence in-situ hybridization should be done when feasible. The clinician should use the information from pathologic examination and cytoge-

netic testing to better classify the disease, predict the prognosis, and hopefully tailor the treatment.

In the future, we will continue to explore the molecular biology and different pathogenetic aspects of the disease to develop a better understanding and to translate the basic science findings into targeted therapies. The new WHO classification may allow us to classify the disease into more homogenous classes, to develop treatments for those subtypes, and to continue refining the classification, as we understand the biology and behavior of the disease.

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