The myelodysplastic syndromes

Abstract

The myelodysplastic syndromes (MDS) are a heterogeneous group of acquired clonal bone marrow disorders characterized by varying degrees of morphological and functional cellular abnormalities involving one or more cell lines. MDS is characterized by impaired, ineffective, proliferation and maturation of hematopoietic progenitor cells resulting in symptomatic anemia, leukopenia, or thrombocytopenia. The clinical course is variable, ranging from a chronic, stable, mildly symptomatic disorder to a disease that compromises the patients quality of life rapidly progresses to acute myeloid leukemia (AML). Infections and/or bleeding are the most frequent causes of morbidity and mortality in patients with MDS. MDS shares many clinical, cytogenetic, and laboratory features with other hematologic disorders including aplastic anemia, the myeloproliferative neoplasms and the acute leukemias. The World Health Organization (WHO) classification of MDS continues to evolve, incorporating clinical, cytogenetic, and molecular studies in an attempt to define MDS and separate it from the myeloproliferative neoplasms, hypoproliferative disorders and the acute leukemias. Finally, secondary causes of bone marrow failure and certain hereditary syndromes can masquerade as MDS. The WHO updated and modified the diagnosis and classification of MDS in 2016. The new classification is controversial and attempts to incorporate new mutational studies while continuing to support the role of morphology in the diagnosis and classification of MDS. Patients with MDS may present with clinical and laboratory features suggestive of reactive, autoimmune or other malignant stem cell disorders. In many instances, the diagnosis of MDS is based on the exclusion of other disorders associated with dysplasia and ineffective hematopoiesis. This chapter discusses the pathogenesis, clinical manifestations, classification, prognostic variables, and specific treatments for MDS.