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Myelodysplastic Syndrome (MDS): Overview & Types

Home> Myelodysplastic Syndrome (MDS)> Overview and Types

What is Myelodysplastic Syndrome?

Myelodysplastic syndrome (MDS) refers to hematological neoplasms that occur when some of the blood-forming cells in the bone marrow fail to function properly. Bone marrow is found in the long bones. Several types of cells are present in the bone marrow: fat cells, blood-forming cells, and related tissues.

The inability of the cells of the bone marrow to produce healthy and mature blood cells results in myelodysplastic disorder.

What Happens in Myelodysplastic Syndrome?

Several causes may explain the occurrence of myelodysplastic syndrome. These are:

Dysfunction in Blood Cell Production

One reason for myelodysplastic syndrome is the dysfunction in blood cell production. In these patients, some bone marrow cells become abnormal and cannot produce new healthy blood cells.

The blood cells formed by these abnormal bone marrow cells have abnormal characteristics and die earlier than normal healthy cells. In addition, the body's immune system destroys some abnormal cells.

Accumulation of Immature Cells (Blasts)

Although blood cells are produced by abnormal bone marrow cells, these are immature and unhealthy and do not perform the functions of healthy cells.

Over time, immature bone marrow cells accumulate in the blood and do not allow the healthy blood cells to perform their function. These immature bone marrow cells in the blood are known as blast cells. Thus, patients experience several symptoms that are attributed to the non-functioning of healthy blood cells.

Who is Affected by Myelodysplastic Syndrome?

The myelodysplasia disease can affect anyone. However, certain people are at increased risk of developing MDS cancer. These individuals include elderly people (>60 years of age), those with a history of treatment with chemotherapy and radiation therapy, those exposed to certain chemicals, e.g., benzene, male gender, people who smoke, those with a family history of myelodysplastic syndrome, and those having genetic syndromes, such as Diamond Blackfan anemia and Fanconi anemia.

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Types of Myelodysplastic Syndromes

Following are the different types of MDS:

1. Myelodysplastic Syndrome (MDS) with single-lineage dysplasia (SLD)

In this type of MDS disease, only one cell type (white blood cells, platelets, or red blood cells) is low in number and has abnormal characteristics. Although dysplasia is reported in one cell type, the patients may have a reduced number of 1 to 2 cell types and have a normal number of other cell types. MDS with single lineage dysplasia is not a very common type. It has the potential to progress to acute myeloid leukemia. The prognosis for this type is good, as the patient may live long, even without treatment.

2. Myelodysplastic syndromes with multi-lineage dysplasia (MLD)

This type is characterized by the presence of dysplasia or abnormality in two or three types of blood cells. The patients experience low levels of ≥1 type of blood cell. The number of blasts in the bone marrow is normal, and there are usually no blasts in the blood.

3. Myelodysplastic syndromes with ring sideroblasts (MDS-RS)

Patients with this type of MDS have reduced numbers of one (MDS-RS-SLD) or more (MDS-RS-MLD) types of blood cells. This condition is characterized by the presence of rings of excess iron in the red blood cells in the bone marrow. For myelodysplastic syndrome diagnosis with ring sideroblasts, ≥15% of the red blood cells in the bone marrow should be ring sideroblasts.

4. Myelodysplastic syndromes with isolated del(5q) chromosome abnormality

This type of MDS is characterized by the absence of chromosome number 5 in the chromosomes of the bone marrow cells. The patients experience dysplasia in ≥1 cell type and have a low number of one or two blood cell types; one of them usually is the red blood cells. This type of MDS usually occurs in elderly women. The patients diagnosed with this MDS type have a good prognosis. The risk of progression of this MDS type to acute myeloid leukemia is very low.

5. Myelodysplastic syndromes with excess blasts

This type of MDS is characterized by a relatively higher number of blasts in the blood or the bone marrow. The patients have low levels of ≥1 blood type and may or may not have severe bone marrow dysplasia. It is a relatively more common type of MDS and has a high risk of progressing to acute myeloid leukemia. The risk of acute myeloid leukemia increases as the number of blasts increases in the bone marrow or the blood.

6. Myelodysplastic syndromes, unclassifiable

It is not a common type of MDS. It is diagnosed when the blood and bone marrow analysis report does not meet the criteria of other types of MDS. In some cases, the blood cells have a normal appearance, but genetic analysis reveals chromosomal changes in the bone marrow cells, which is consistent with MDS.


What are the Stages of Myelodysplastic Syndromes?

Although there are no actual stages of myelodysplastic syndrome, unlike other types of cancers, certain scoring systems are used to classify the MDS into various risk categories. Some of the common scoring systems are:

Revised International Prognostic Scoring System (IPSS-R): Several factors are considered while categorizing the disease into a particular risk category. These factors include blast percentage in the bone marrow, chromosomal abnormalities (type and number) in the cells, platelet levels in the blood, red blood cell levels in the blood, and neutrophil levels in the blood.

Scores are provided for each of the above factors, and the cumulative score defines the category of the diseases. Patients with low scores have a more favorable prognosis compared with patients with high scores. The categories include very low, low, intermediate, high, and very high risks. The categories are also helpful in planning the treatment.

WHO Prognostic Scoring System (WPSS): This is another scoring system used to categorize MDS based on risk. The factors considered while calculating the scores under this system are the type of MDS present according to the WHO classification, the requirement of blood transfusion, and the type of chromosomal abnormality (defined as poor, intermediate, and good).

The scores are indicated for each factor, and the cumulative score defines the disease category. The risk categories under the WPSS system are similar to those in the IPSS-R system.

Conclusion

MDS is characterized by the inability of the cells of the bone marrow to produce mature, healthy blood cells. Based on the number of types of blood cells affected, the disease is classified into single lineage and multi-lineage. Although it may occur in any individual, elderly people, people who smoke, have a history of chemotherapy or radiation therapy, have a family history of MDS, and have exposure to toxic chemicals are at increased risk for developing MDS.

Frequently Asked Questions

Is MDS a serious condition?

Some of the types of MDS are serious and have the potential to progress into acute myeloid leukemia. Patients may also be affected by less serious forms of MDS that may not require treatment.

In patients with MDS, the bone marrow cells are unable to produce healthy, mature blood cells. Patients with this condition have low levels of either one or more mature blood cells.

Although there is no cure for MDS, appropriate treatment may slow its progression and manage the symptoms. The only curative option available for MDS is the stem cell transplant. However, it is challenging as most patients with MDS are elderly and may not fulfill the criteria for stem cell transplant.

The survival rate of MDS depends upon several factors, the most significant among them being the type of MDS. Other factors affecting the survival rate are the severity of myelodysplastic syndrome symptoms, progression of the disease into other hematological malignancies, like acute myeloid leukemia, and response to treatment.

It is not possible to prevent MDS. That said, with appropriate myelodysplastic syndrome prevention measures, it may be possible to reduce its risk.

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