Myelodysplastic syndromes (MDS)

Abstract:
Myelodysplastic syndromes are a group of clonal bone marrow diseases, that are characterized by defective maturation of the hematopoietic cells. Myelodysplastic syndromes are often confused with myeloproliferative syndromes because the terms are similar. At least one of the peripheral blood counts is decreased, i.e., anemia, thrombocytopenia, or neutropenia. A combination of two cytopenias or pancytopenia can occur. The bone marrow is typically hypercellular. In addition, a maturation defect of one or all cell lines occurs, which typically is expressed as macrocytosis by the erythrocytes in the peripheral blood. The discrepancy between a peripheral cytopenia and a hypercellular bone marrow suggest ineffective hematopoiesis.
Patients with MDS are usually 60 years of age or older. The Incidence of MDS increases with age. The prognosis depends on the morphological picture and the presence of cytogenetic abnormalities.

Morphological classification of MDS based on the French-American-British (FAB) classification:

Morphological subtype	Percentage of blasts		Other abnormalities and annotations
	Bone marrow	Blood
Refractory anemia (RA)	<5%	<= 1%	average life expectancy is very variable, on the average 2.5 years.
RA with ringed sideroblasts (RARS)	< 5%	<= 1%	>15% ringed sideroblasts average life expectancy approx. 5 years
RA with an excess of blasts (RAEB)	5-20%	<5%	average life expectancy <1 year
RAEB in transformation (RAEB-T)	20-30% or Auer rods	>5%	average life expectancy <1 year
chronic myelomonocytic leukemia	<20%	<5%	Monocytosis >1.0 x 109/L splenomegaly average life expectancy of 1 to 5 years