The Myelodysplastic syndrom is a group of diseases and conditions that affect how blood is made. These diseases were formerly known as preleukemia, mostly because sometimes they can lead to leukemia. Often, its name is shortened to MDS.
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.
Most of the people who have these conditions are 60 years or older, but younger people can get it too, especially if they went through a form of chemotherapy. Most of the suffers die from the disease, usually after six to thirty months. The only known cure is a stem cell transplant. About a third of those suffering contract leukemia within a few months to a few years.