There are several kinds (subtypes) of MDS. Doctors classify MDS subtypes according to different factors. Doctors often use one of two systems to classify them: the French, American, British (FAB) classification system or World Health Organization (WHO) classification system.
Doctors also use the International Prognostic Scoring System (IPSS) to more narrowly define the degree of the disease's severity, determine patient risk factors and plan treatment.
The table below shows the FAB classification system used by many doctors. The five FAB subtypes are based on bone marrow appearance and blood cell counts.
|Refractory anemia (RA)||
|Refractory anemia with ringed sideroblasts (RARS)||
|Refractory anemia with excess blasts (RAEB)||
|Refractory anemia with excess blasts in transformation (RAEB-T)||
|Chronic myelomonocytic leukemia (CMML)||
A newer system sometimes used by doctors is the WHO classification system. It classifies MDS according to factors that differ from those of the FAB system:
- Considers molecular and chromosomal (cytogenetic) data
- Defines RAEB-T to be a leukemia rather than a subtype of MDS
- Defines patients with more than 20 percent blasts in marrow as having acute myeloid leukemia (AML)
- Includes the category of myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN)
- Includes juvenile myelomonocytic leukemia (JMML) and chronic myelomonocytic leukemia (CMML) in the MDS/MPD category
- Includes the following subtypes:
- 5q- syndrome
- Refractory cytopenia with multilineage dysplasia (RCMD)
- Unclassifiable MDS (MDS-u)