• Clinical science

Myelodysplastic syndromes


Myelodysplastic syndromes (MDS) are a group of hematological cancers in which malfunctioning pluripotent stem cells lead to hypercellularity and dysplasia of the bone marrow. This, in turn, leads to cytopenia of one or more cell lines (thrombocytopenia, erythrocytopenia, leukocytopenia). Most cases of MDS have a primary, idiopathic etiology, while a minority of cases are secondary to an underlying cause. MDS usually affects elderly patients and has a slowly progressive course. Clinical features vary depending on the type of MDS and the affected cell lines, and may include signs of anemia (e.g., fatigue, weakness, pallor), recurrent infections, and/or petechial bleeding. Diagnosis of MDS requires blood tests, bone marrow biopsy, and possibly genetic analysis. While mild cases may be closely monitored, severe disease typically requires blood transfusions supplemented with erythropoietin, vitamins, and, in some cases, granulocyte colony-stimulating factor. Medical therapy (e.g., chemotherapy or immunosuppressants) may also help to manage the disease, but allogenous stem cell transplantation is the only curative treatment. In 30% of cases, the disease progresses to acute myeloid leukemia.




WHO Classification of Primary Myelodysplastic Syndromes

  • The WHO classification distinguishes between eight different primary myelodysplastic syndromes, based on the number of dysplastic cell lines and the percentage of blasts in the bone marrow, among other criteria
  • The most common types are refractory cytopenia with multilineage dysplasia, refractory anemia with ringed sideroblasts, and refractory cytopenia with unilineage dysplasia
Syndrome Blood test Bone marrow examination Percentage of MDS

Refractory cytopenia with unilineage dysplasia (RCUD)

Deficient in one type of cell with normal numbers of other cells

Cells that mature to produce the following cells look abnormal:

  • Proerythroblasts and polychromatic erythroblasts
  • Myeloblast and progranulocyte
  • Megakaryoblasts and megakaryocytes
Refractory anemia with ringed sideroblasts (RARS)

Low RBC count

  • Only 10% of cells look abnormal.
  • 15% of early cells contain rings of iron deposits around the nucleus. These are called ringed sideroblasts.
Refractory cytopenia with multilineage dysplasia (RCMD)

Deficient in at least two types of cells

  • The precursors of at least two types of cells look abnormal (dysplasia)
  • Ringed sideroblasts may or may not be present
  • Very low number of blast cells (≤ 5%)
  • Blasts do not contain Auer rods
Refractory anemia with excess blasts-1 (RAEB-1)
  • Deficient in one or more types of cells
  • Blasts are present in blood (≤ 5%)
  • The precursors of one or more types of cells look abnormal.
  • Slightly increased number of blast cells (≤ 10%)
  • Blasts do not contain Auer rods
Refractory anemia with excess blasts- 2 (RAEB-2)
  • Deficient in one or more types of cells
  • Blast cells that normally develop into WBCs are present (5–20%)
  • The precursors of one or more types of cells look abnormal.
  • Increased number of blast cells (10–20%)
  • Blasts may contain Auer rods
Myelodysplastic syndrome, unclassified (MDS- U)
  • Deficient in any one type of cell
  • Only 10% of the respective precursor cells look abnormal
  • Cells contain at least one chromosomal abnormality
  • Very few blast cells (≤5%)
Uncommon; therefore unknown
Myelodysplastic syndrome associated with isolated del(5q)
  • A small part of chromosome 5 is missing
  • Very few blast cells (≤5%)


Clinical features

  • Asymptomatic in 20% of cases
  • Dependent on the affected cell line
  • Hepatosplenomegaly (uncommon)





The therapeutic approach depends on a patient's presentation, age, and comorbidities. More aggressive therapy (e.g., chemotherapy, stem cell transplantation) is generally reserved for younger, healthier patients.



Depending on the chromosomal aberrations detected in pluripotent stem cells, up to 30% of MDS cases may progress to acute myelogenous leukemia.


We list the most important complications. The selection is not exhaustive.

last updated 10/16/2018
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