Globin chain synthesis in myelodysplastic syndromes

Clonal hematopoiesis and acquired genetic abnormalities of the red cell: An historical review

Several syndromes affecting the red cell that mimic those induced by germline mutations may result from a somatic mutation that accompanies a myeloid malignancy. These syndromes are most notable in cases of myelodysplastic syndrome, but they are not limited to any one category of myeloid neoplasm. Their occurrence in males exceed the male predominance that is evident in myeloid neoplasms. The syndromes include disorders of globin chain synthesis (α- and β-thalassemia), heme synthesis (erythropoietic porphyria and erythropoietic uroporphyria), red cell membrane structure (elliptocytosis and spherocytosis), red cell enzyme activity (pyruvate kinase deficiency, glucose-6-phosphate dehydrogenase deficiency) and lowered expression of red cell ABO blood group antigens. This historical review describes the path to uncovering these acquired syndromes and their causal somatic mutations, where known. These syndromes often go unrecognized because of the dominant concern of the primary neoplasm. They may add to the healthcare needs of the patient.

Microcytosis in agnogenic myeloid metaplasia: Prevalence and clinical correlates

Microcytosis is a characteristic laboratory feature for both iron deficiency anemia and thalassemia. It is also infrequently seen in "anemia of chronic disease" that accompanies a spectrum of chronic conditions including rheumatoid arthritis, polymyalgia rheumatica, diabetes mellitus, connective tissue disease, and protracted infection. In addition, there is a well established but pathogenetically obscure association of microcytosis with Hodgkin's lymphoma, Castleman's disease, and renal cell carcinoma. In the current study, we show that microcytosis is a frequent laboratory feature in agnogenic myeloid metaplasia and investigate its clinical relevance in the particular setting.

Clinical features of MDS

MDS is primarily a disease of the elderly. Cases who give a history of exposure to X-rays, cytotoxic drugs or leukaemogenic chemicals may be younger. Many cases of MDS present because of an incidental blood count. The most prominent clinical features are those of anaemia, neutropenia, thrombocytopenia. Because haemopoietic tissue is also dysfunctional the pathological effect is often greater than the figures would suggest, even leading to infection of bleeding with normal neutrophil or platelet counts. Occult abscesses are a particular feature. Despite documented abnormalities of the lymphoid system, neither infections characteristic of T-cell immunodeficiency nor autoimmunity is a problem. The proliferation of monocytes in CMML leads to organomegaly, leukaemia cutis, serous effusions and vasculitic lesions caused by the mishandling of circulating immune complexes. Cancer is no commoner than in age-matched controls, but coincident lymphoid tumours do occur. Many patients require long-term blood transfusion and will run into problems of iron overload unless precautions are taken.