Myelodysplastic syndrome" - MDS- is the name given to a group of clonal disorders of hematopoietic stem cells characterized by dysplasia of blood and bone marrow cells with hematopoietic insufficiency and increased risk of developing acute myeloid leukemia. The leading finding is usually anemia, and often bi- or pancytopenia. The bone marrow is often normo- or hypercellular, in about 10% of cases hypocellular. Diagnostically suggestive are dysplasia signs of one or more cell series. At least 10 % of the cells in a row must show clear signs of dysplasia for the diagnosis of MDS to be made.
In approximately 90% of cases, the cause cannot be determined with certainty (primary MDS). In 10% of cases (secondary MDS or also therapy-associated MDS > 80% chromosomal aberrations), previous chemotherapy and/or radiotherapy are known and probably causative.