Molecular Basis of Lymphoid and Myeloid Diseases

Publisher Summary This chapter focuses on the molecular basis of lymphoid and myeloid diseases. Disorders of lymphocytes include deficiency of lymphocytes (lymphopenia) and over proliferation of lymphocytes. Over proliferation of lymphocytes is due to either reactive proliferation of lymphocytes (lymphocytosis) or to neoplastic problems. On the other hand, myeloid disorders include anemia, neutropenia, and Myelodysplastic Syndromes (MDS). Anemia is a condition in which the blood contains a lower than normal number of Red Blood Cells (RBCs) or RBCs that do not contain enough hemoglobin. Neutropenia may occur as chronic idiopathic neutropenia or severe congenital neutropenia. Chronic idiopathic neutropenia is defined as any RBC destruction. MDS are diagnosed at a rate of 3.6/100,000 people in the United States. It occurs primarily in older patients (>60 years), but occasionally in younger patients. Anemia, bleeding, easy bruising, and fatigue are common and splenomegaly or hepatosplenomegaly may occasionally be present. The MDS are characterized by abnormal bone marrow and blood cell morphology. It is classified according to cellular morphology, etiology, and clinical features. The morphological classification is largely based on percent myeloblasts in the bone marrow and blood, the type of myeloid dysplasia, and the presence of ringed side-roblasts. Myelodysplastic/myeloproliferative diseases have features of both myelodysplastic syndromes and myeloproliferative disorders. The three main types of myelodysplastic/myeloproliferative diseases are Chronic Myelomonocytic Leukemia (CMML), Juvenile Myelomonocytic Leukemia (JMML), and Atypical Chronic Myelomonocytic Leukemia (aCML).