Types of Myelodysplastic Syndromes

NYU Langone doctors specialize in diagnosing all types of myelodysplastic disorders, in which the bone marrow—the soft, spongy tissue in the center of the bones—does not produce enough healthy blood cells.

Myelodysplastic syndromes occur when stem cells, which are immature blood-forming cells in the bone marrow, are defective and do not mature into one or more types of healthy blood cells. These can include red blood cells, which carry oxygen to the body’s tissues, as well as white blood cells, which help fight infections, and platelets, which help blood to clot.

When a person has a reduced number of red blood cells, he or she has a condition called anemia, which can lead to weakness and fatigue. The occurrence of too few white blood cells, which is called leukopenia, can lead to infections. A reduced number of platelets, called thrombocytopenia, can cause problems with bleeding.

Myelodysplastic syndromes are often categorized by the number, type, and appearance of cells in the bone marrow and in the blood. Myeloblasts, also called blast cells, are young blood cells produced by stem cells. The percentage of myeloblasts in the bone marrow is important, because this can indicate how likely the condition is to progress to acute myeloid leukemia, or AML.

An increased number of blast cells can also interfere with the production of healthy, mature red and white blood cells and platelets.

Pinpointing abnormalities in chromosomes, the parts of cells that carry genetic information, can also help identify some types of myelodysplastic syndromes.

Refractory Anemia with Ringed Sideroblasts

With this type of myelodysplastic syndrome, the level of red blood cells is low, and at least 15 percent of them are abnormal cells called sideroblasts. These are red blood cells that have rings of iron deposits around their centers. The levels of white blood cells and platelets are normal.

The percentage of blast cells in a healthy person is less than 5 percent. In a person with refractory anemia with ringed sideroblasts, about 10 percent of the cells in the bone marrow are blast cells. This condition is considered slowly progressive or low grade, meaning it is less likely to progress to AML.

Refractory Cytopenia with Unilineage Dysplasia

Refractory cytopenia with unilineage dysplasia is a blood disorder in which the level of one type of blood cell is low, but the levels of the other two types of blood cells are normal.

Most commonly, red blood cell levels are low, while white blood cell and platelet levels are healthy. This is called refractory anemia.

Other types of refractory cytopenia with unilineage dysplasia include refractory neutropenia, in which the level of neutrophils, a type of white blood cell, is low. There is also refractory thrombocytopenia, which refers to a low level of platelets.

When the bone marrow is observed under a microscope, about 10 percent of the low-level cells look abnormal, or dysplastic. The amount of blast cells is usually less than 5 percent, which is normal.

This form of myelodysplastic syndrome is considered slowly progressive or low grade and is less likely to progress to AML.

Refractory Cytopenia with Multilineage Dysplasia

With this form of myelodysplastic syndrome, the levels of two different blood cell types are low. Also, these cells appear misshapen in the bone marrow.

About 15 percent of cells are ringed sideroblasts. Less than 5 percent of the cells in the bone marrow are blasts.

This form of myelodysplastic syndrome can sometimes progress to AML. The risk depends on how low blood cell levels are, along with the percentage of blasts in the bone marrow and the number and type of abnormalities in the chromosomes.

Refractory Anemia with Excess Blasts-1

People with refractory anemia with excess blasts-1 have reduced levels of one or more types of blood cells. Additionally, between 5 percent and 10 percent of cells in the bone marrow are blast cells. In the blood stream, 5 percent of cells may be blast cells.

This type of myelodysplastic syndrome can progress to AML.

Refractory Anemia with Excess Blasts-2

People with refractory anemia with excess blasts-2 have a reduced amount of one or more types of blood cells.

Blasts make up 10 percent to 20 percent of the cells found in the bone marrow. In the blood stream, between 5 percent and 19 percent of cells may be blasts. The blasts may contain Auer rods, which are clumps of abnormal material that form needle-like structures.

The odds of refractory anemia with excess blasts-2 progressing to AML are higher than with refractory anemia with excess blasts-1.

Myelodysplastic Syndrome, Unclassified

People with this type of myelodysplastic syndrome have low levels of red blood cells, white blood cells, or platelets. Less than 10 percent of these cells in the bone marrow look abnormal under a microscope, and 5 percent of cells are blasts.

A chromosomal abnormality associated with myelodysplastic syndrome may be identified in people with this condition. However, other signs of it, such as the percentage of blasts or low blood cell levels, do not fit in any other myelodysplastic syndrome category.

This form of myelodysplastic syndrome is so rare that the likelihood of progression to AML is unknown.

Myelodysplastic Syndrome Associated with Isolated Deletion 5q

With this form of myelodysplastic syndrome, the bone marrow contains cells in which part of chromosome 5 is missing. The percentage of blasts in the bone marrow is usually less than 5 percent. Red blood cell levels are low in the bloodstream, but white blood cell levels are normal. Platelet levels may be increased.

People with myelodysplastic syndrome associated with Isolated Deletion 5q have a low risk of the condition progressing to AML.