Myelodysplastic Syndromes

Types

Myelodysplastic syndromes describes a group of similar diseases that have low blood counts and a risk of progressing into AML. They can be divided into five main types:

Refractory anemia

Refractory anemia (shortage of red blood cells) does not respond to treatment with vitamins or iron. It may be considered an "early" kind of MDS. There are no immature (blast) cells in the blood. In the marrow, blast counts are either normal or close to normal.

Refractory cytopenias with multilineage dysplasia

This type of MDS is similar to refractory anemia, but other kinds of cells besides red blood cells are also low. The risk of developing leukemia or a serious complication related to low blood counts is higher with this condition, compared to refractory anemia.

Refractory anemia with excess blasts (RAEB)

In RAEB, increased blasts are present in the bone marrow and some may enter the
bloodstream. The higher the number of blasts, the greater the possibility that RAEB will become acute leukemia. RAEB is considered a higher-risk type of MDS.

Refractory anemia with ring sideroblasts (RARS)

Ring sideroblasts are developing red blood cells that get their name from a dark circle caused by abnormal iron deposits. People with ring sideroblasts sometimes have too much iron in their bodies. Ring sideroblast cells can be caused by other medical conditions. Most people with RARS have anemia but not other low blood counts.

MDS associated with deletions of the long arm chromosome 5

This form of MDS is associated with an abnormal chromosome 5 that is missing part of its long arm (called "q"). It is not inherited and is only present in bone marrow and blood cells. Anemia is common, and the platelet count may be normal or perhaps elevated. This form is less likely to become leukemia.

Several variations of these five main types of MDS exist.

Prognostic Scoring System

The type of MDS is important in predicting the course of the disease. The International Prognostic Scoring System is used to help predict the course of MDS. Besides age and physical function, this system looks at three factors that have been shown to influence the course of MDS:

• Percentage of bone marrow blasts (the higher the percentage, the poorer the predicted outcome)
• Karyotype (kind of chromosomal abnormalities)
• Cytopenia (number or types of blood cell deficiencies)