Patients with MDS can develop severe anemia and require blood transfusions. In some cases, the disease worsens and the patient develops cytopenias (low blood counts) caused by progressive bone marrow failure. The outlook in MDS depends on the type and severity. Many people live normal lifespans with MDS.
The myelodysplastic syndromes are all disorders of the hematopoietic stem cells in the bone marrow (only related to myeloid lineage). In MDS, hematopoiesis (i.e., blood production) is disorderly and ineffective. The number and quality of blood-forming cells decline irreversibly, further impairing blood production. The mean age of onset of MDS is 68 years.
The best prognosis is seen with RA and RARS, where some non-transplant patients live more than a decade (the average is on the order of three to five years, although long-term remission is possible if a bone marrow transplant is successful). The worst outlook is with RAEB-T, where the mean life expectancy is less than 1 year. About one quarter of patients develop overt leukemia. The others die of complications of low blood count or unrelated disease. The International Prognostic Scoring System is another tool for determining the prognosis of MDS, published in Blood in 1997. This system takes into account the percentage of blasts in the marrow, cytogenetics, and number of cytopenias.