Epidemiology Idiopathic MDS is a disease of the elderly; the mean age at onset is 68 years. There is a slight male preponderance. MDS is a relatively common form of bone marrow failure, with reported incidence rates of 35 to 100 per million persons in the general population and 120 to 500 per million in the elderly. MDS is rare in children, but monocytic leukemia can be seen. Therapy-related MDS is not age-related and may occur in as many as 15% of patients within a decade following intensive combined modality treatment for cancer. Rates of MDS have increased over time,. | Chapter 102. Aplastic Anemia Myelodysplasia and Related Bone Marrow Failure Syndromes Part 13 Epidemiology Idiopathic MDS is a disease of the elderly the mean age at onset is 68 years. There is a slight male preponderance. MDS is a relatively common form of bone marrow failure with reported incidence rates of 35 to 100 per million persons in the general population and 120 to 500 per million in the elderly. MDS is rare in children but monocytic leukemia can be seen. Therapy-related MDS is not age-related and may occur in as many as 15 of patients within a decade following intensive combined modality treatment for cancer. Rates of MDS have increased over time due to the recognition of the syndrome by physicians and the aging of the population. Etiology and Pathophysiology MDS is caused by environmental exposures such as radiation and benzene other risk factors have been reported inconsistently. Secondary MDS occurs as a late toxicity of cancer treatment usually with a combination of radiation and the radiomimetic alkylating agents such as busulfan nitrosourea or procarbazine with a latent period of 5-7 years or the DNA topoisomerase inhibitors 2 years . Both acquired aplastic anemia following immunosuppressive treatment and Fanconi s anemia can evolve into MDS. MDS is a clonal hematopoietic stem cell disorder leading to impaired cell proliferation and differentiation. Cytogenetic abnormalities are found in about half of patients and some of the same specific lesions are also seen in frank leukemia aneuploidy is more frequent than translocations. Both presenting and evolving hematologic manifestations result from the accumulation of multiple genetic lesions loss of tumor suppressor genes activating oncogene mutations or other harmful alterations. Cytogenetic abnormalities are not random loss of all or part of 5 7 and 20 trisomy of 8 and may be related to etiology 11q23 following topoisomerase II inhibitors chronic myelomonocytic leukemia is often associated with t 5 .
