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MDS Subtypes

There are several kinds (subtypes) of MDS. The subtype is determined from the results of the blood and bone marrow tests.

The classification of myelodysplastic syndromes has evolved considerably over the last several decades. In 1982, the French-American-British (FAB) Work Group devised a system for classifying myelodysplastic syndromes. The FAB classification divided myelodysplastic syndromes into five subtypes based on the percentage of blasts present in the bone marrow and the peripheral blood, the number of ring sideroblasts and the degree of monocytosis (elevated number of white blood cells).

In 2001, the World Health Organization (WHO) proposed an alternative classification that was a modified version of the original FAB classification. The WHO classification incorporated molecular and cytogenetic factors. Since then, the WHO classification has been updated twice, once in 2008 and again in 2016 (see Table 1 on page 9). The 2016 WHO classification is more commonly used today.

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.


WHO Classification

The current WHO classification guidelines identify six subtypes of MDS based on the results of blood and bone marrow test. It classifies MDS according to factors that differ from those of the FAB system:

  • MDS with single lineage dysplasia (MDS-SLD)
  • MDS with ring sideroblasts (MDS-RS)
    • Single lineage dysplasia (MDS-RS-SLD)
    • Multilineage dysplasia (MDS-RS-MLD)
  • MDS with multilineage dysplasia (MDS-MLD)
  • MDS with excess blasts (MDS-EB)
    • MDS with excess blasts-1 (MDS-EB-1)
    • MDS with excess blasts-2 (MDS-EB-2)
  • MDS with isolated del(5q)
  • MDS, unclassifiable (MDS-U)

Myelodysplastic Syndromes/Myeloproliferative Neoplasms (MDS/MPN) Classification. The WHO also has a category called “myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN).” This category includes subtypes that have both dysplastic and proliferative features. “Dysplastic” refers to the abnormal growth or development of cells in the bone marrow, and “proliferative” means the bone marrow produces too many blood cells. Visit Myeloproliferative Neoplasms to learn more. 



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