Myelodysplastic syndromes affect the bone marrow stem cells. The production of blood does not rely on good stem cells, but ones that have been modified genetically. This means that the production of red blood cells, sometimes of white blood cells and blood platelets changed. The production becomes inefficient, or goes wrong altogether. Most of the time, this manifests in anemia - not having enough blood. Depending on the severity of the condition, it can also cause hemorrhages and infections with fever.