Accumulation of both genetic and epigenetic changes in hematopoietic stem cells is considered the background for development of MDS. In the early stages of the disease, there is increased apoptosis, but as the disease progresses to high-risk MDS or AML there is an accumulation of chromosomal breakage, point mutations and promoter hypermethylation of tumor suppressor genes, resulting in a more aggressive and proliferative disease. The clinical symptoms are anemia, repeated infections and bleeding episodes associated with the dysfunctional bone marrow.