Myelodysplastic syndromes: what they are, causes and treatments

Myelodysplastic syndromes are a form of cancer, the prognosis of which depends on various factors. In general terms, the survival of low-risk patients is eight years. In those of high risk, of less than a year.

Last update: 04 October, 2021

A group of blood cell disorders is known as “myelodysplastic syndromes.” These alterations occur when blood-producing cells, which are in the marrow of the bones, become abnormal.

Sometimes such cells are badly formed and other times they malfunction. The truth is that this leads to lower counts of one or more types of blood cells. Myelodysplastic syndromes are considered a form of cancer.

Types of myelodysplastic syndromes

Abnormal blood-forming cells produce myelodysplastic syndromes.

The World Health Organization has classified myelodysplastic syndromes into six groups. The criteria used for this cataloging, among others, are the following:

  • Percentage of cells that look abnormal under the microscope; that is, they have dysplasia.
  • Number of results with low blood cell counts (cytopenia).
  • Percentage of young red blood cells that have iron deposits around the nucleus; that is, they are “ring sideroblasts.”
  • The percentage of very young blood cells (blasts) in the bone marrow or blood.
  • Presence of certain chromosome alterations in the cells of the bone marrow.

Based on these factors, the six types of myelodysplastic syndromes are defined, which are the following.

MDS with multilineage dysplasia (MDS-MLD)

This is the most common type of myelodysplastic syndromes. It is defined by the following criteria:

  • At least 10% of the blood cells in the bone marrow look abnormal under a microscope (dysplasia). The cells can be red blood cells, white blood cells, or platelets. At least two of these guys must meet that criteria.
  • There is a low count of at least one type of blood cell.
  • The number of very young cells (blasts) in the bone marrow is normal. On the other hand, in the blood it is very low or there is none.

MDS with Unilineage Dysplasia (MDS-SLD)

This is not a very common modality in myelodysplastic syndromes. People who suffer from it often survive for a long time, even without treatment. The criteria that define it are the following:

  • At least 10% of one of the types of blood cells in the bone marrow have dysplasia.
  • There are low counts of two types of blood cells.
  • The number of very young cells (blasts) in the bone marrow is normal. On the other hand, in the blood it is very low or there is none.

MDS with ring sideroblasts (MDS-RS)

This is another of the rare types of myelodysplastic syndromes and his prognosis is one of the most favorable. The main characteristic is that there are two factors:

  • At least 15% of red blood cells have iron deposits around the nucleus; that is, they are “ring sideroblasts.”
  • If the previous criterion is not met, at least 5% must have this condition and, in addition, present a mutation in the SF3B1 gene.

MDS with excess blasts (MDS-EB)

This modality represents one in four cases of myelodysplastic syndromes. The factors that characterize it are the following:

  • There are more very young cells (blasts) than normal in the bone marrow or blood.
  • There is a low count of at least one type of blood cell.
  • There may or may not be bone marrow dysplasia.

MDS with del (5q) isolated

This is a form of myelodysplastic syndromes that affects older women more, but, in general, it is not very common. In any case, the prognosis is favorable. The main characteristics are the following:

  • A part of chromosome number 5 is missing in bone marrow cells.
  • There is a low count of at least one type of blood cell.
  • There is dysplasia in at least one of the bone marrow cell types.

MDS, unclassifiable (MDS-U)

Within this group of myelodysplastic syndromes are those conditions in which the criteria of the other groups are not fully met. It is not very common and has not been studied in detail, so the prognosis is unknown.

Causes of myelodysplastic syndromes

Under normal conditions, the bone marrow produces new blood cells that mature over time. When myelodysplastic syndromes occur, some factor appears that interrupts this process.

When this happens, blood cells begin to develop abnormally and die in the bone marrow or when they enter the bloodstream. A point is reached where there are more defective cells than healthy ones And this leads to problems like anemia, leukopenia, and thrombocytopenia.

Myelodysplastic syndromes can be caused by cancer treatments (chemotherapy and radiation therapy) or by exposure to toxic substances such as benzene. Nevertheless, in most cases the specific cause of these disorders is unknown.

Symptoms of myelodysplastic syndromes

It is relatively common that people with myelodysplastic syndromes do not experience any symptoms at first. However, over time, manifestations such as the following appear:

  • Tiredness and fatigue.
  • Feeling short of breath
  • Very pale skin, as an effect of anemia.
  • Easy bruising or bleeding. This is the effect of thrombocytopenia, or low platelet count. That is, small red spots, the size of a pinhead, under the skin.
  • Frequent infections. They are caused by a low white blood cell count or leukopenia.

Risk factor’s

There are some conditions that can increase the risk of myelodysplastic syndromes. Among these factors are the following:

  • Previous chemotherapy or radiotherapy treatment. They are common cancer treatments and increase the risk of myelodysplastic syndromes.
  • Exposure to heavy metals. They include mercury, lead, etc.
  • Exposure to some chemicals. Among these are pesticides, fertilizers, tobacco smoke, solvents such as benzene, etc.
  • Advanced age. These types of syndromes are more common in people over 60 years of age.

How is a myelodysplastic syndrome diagnosed?

A complete physical exam is performed to diagnose myelodysplastic syndromes.

Diagnosis of myelodysplastic syndromes begins with a complete physical exam and an interview to find out the health history. Typically, a Complete Blood Count (RSC) is ordered in the first instance.

The RSC allows to determine the number of red, white blood cells and platelets, as well as the amount of hemoglobin, among other aspects. These data are essential. From them, other tests such as the following are likely to be requested:

  • Peripheral blood smear.
  • Cytogenetic analysis.
  • Biochemical studies of blood.
  • Bone marrow aspiration and biopsy.

Once the biopsy is done, the fabric may undergo one or more of the following tests:

  • Immunocytochemical test.
  • Immunophenotyping.
  • Flow cytometry.
  • Fluorescent in situ hybridization (FISH).

How are myelodysplastic syndromes treated?

Standard treatment for myelodysplastic syndromes includes three strategies: support, drugs and chemotherapy with transplantation. Let’s see, in general terms, what each of them consists of:

  • Supportive medical care. It includes measures such as blood transfusion therapies, administration of erythropoiesis-stimulating medications (ESAs), and antibiotic therapy.
  • Drug therapy. It includes immunosuppressive therapy, chemotherapy to prevent acute myeloid leukemia, and the administration of drugs such as lenalidomide, azacitidine, and decitabine.
  • Stem cell transplant chemotherapy. It involves the administration of drugs to kill cancer cells and stem cell transplantation to replace blood-forming cells.

Currently, research and clinical trials are underway for new cancer treatments. A person affected by any of the myelodysplastic syndromes may consider the option of participating in them.

The course of myelodysplastic syndromes depends on the particular situation

People with myelodysplastic syndromes are at significant risk of developing complications such as anemia, recurrent infections, and excessive bleeding. Also, this often progresses to acute myeloid leukemia.

The prognosis for each person will depend on the type of myelodysplastic syndrome and the associated complications.. In general, the evolution is worse to the extent that there are more risk factors involved.

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