Myelodysplastic syndromes, or MDS, are a group of rare blood disorders associated with faulty
development of blood cells in the bone marrow. MDS can affect individuals of all ages, but
it’s more common after the age of 60.
Blood cells develop from hematopoietic stem cells, through a process called hematopoiesis.
This involves a number of divisions, and eventually, results in three types of blood cells: red
blood cells, which carry oxygen around our bodies, white blood cells to help fight disease
causing pathogens, and platelets that help form clots to stop bleeding. Once these cells
are fully mature, they leave the bone marrow and enter the bloodstream.
In MDS, hematopoietic stem cells are damaged, so they give rise to faulty blood cells, which
don’t mature, but instead persist as immature cells, called blasts. These immature blood
cells usually die in the bone marrow or soon after they go into the blood, so you can’t
really count on them to do the job of mature blood cells. As the condition progresses,
immature blood cells gradually take over the bone marrow, which displaces and reduces the
normal ones.
In most cases, the cause of MDS is not known. When this happens, it's classified as primary
MDS. In rare cases, they can be caused by chemo or radiation therapy, and this is called
secondary MDS.
MDS comprises a spectrum of diseases with differing potential for remaining stable or
progressing to acute myeloid leukemia, or AML. The most common feature of MDS is anemia,
caused by low red blood cell levels. Symptoms of anemia include dizziness, irritability,
headaches, and pale skin. Low white blood cell levels increase the risk of bacterial
and fungal infections. Finally, low levels of platelets cause excessive bruising following
minimal injury and easy bleeding. Now, MDS usually worsens with time, as normal bone
marrow function diminishes. 40-50 percent of the time, MDS deteriorates into a form
of cancer known as acute myeloid leukemia, or AML. This happens when there are more than
20% blasts in the bone marrow.
Diagnosis requires a variety of specialized tests including complete blood counts, a peripheral
blood smear, as well as bone marrow aspiration and biopsy. On a complete blood count, there
may be low levels of one, two or all of the three blood cell types. On a peripheral blood
smear, there may be big and oval-shaped red blood cells and abnormal white blood cells
and platelets. The bone marrow sample may show an increase in cell count with dysplastic
changes in the three blood cell types. Chromosome analysis may find genetic abnormalities in
affected cells.
Treatment of patients is dependent on their clinical risk status, like their risk of developing
leukemia or remaining stable. Patients’ risk status is determined by their complete
blood counts, the proportion of immature cells, or blasts, in the marrow, and the type of
chromosome abnormalities present in their bone marrow cells. This information is used
to generate a score known as the International Prognostic Scoring System-Revised for MDS.
Other features now being evaluated are the presence of mutations in the patients’ cells,
some of which are associated with a poorer prognosis. Treatment of lower risk patients
is generally aimed at improving their blood counts. Growth factors like erythropoietic
growth factors can be given weekly to stimulate the production of red blood cells. In addition
patients with a chromosomal abnormality known as 5q- can be effectively treated with the
drug lenalidomide. In some cases, people with MDS respond to immunosuppressive therapy with
anti-thymocyte globulin. Treatment of higher risk patients is aimed at preventing the patients’
disease from progressing to leukemia. Standard treatment includes the use of hypomethylating
agents like azacitidine or decitabine. In addition, for these patients a bone marrow
stem cell transplant from a healthy donor may be an option and is the only curative
treatment for MDS.
Some treatment for MDS is also supportive, and involves red blood cell transfusions to
correct the anemia, platelet transfusions to treat or prevent serious bleeding, and
antibiotics to treat or prevent infections. Sometimes multiple transfusions may cause
an iron buildup in the body, so an iron chelating agent, like deferasirox, may be needed to
eliminate it from the body.
All right as a quick recap, myelodysplastic syndromes, or MDS are a group of rare blood
disorders where blood cells don’t mature properly in the bone marrow. In most cases,
the cause is unknown. Complications of MDS are either chronic low blood counts or the
potential to develop acute myeloblastic leukemia, when there are more than 20% blasts in the
bone marrow. MDS is associated with symptoms of anemia, easy bruising, bleeding, and increased
susceptibility to infections. Diagnosis requires complete blood counts, a peripheral blood
smear, bone marrow aspiration and biopsy. Treatment depends on the patients’ risk
status and in addition to specific drugs includes red blood cell transfusions to correct the
anemia, platelet transfusions to treat or prevent serious bleeding, and antibiotics
to treat or prevent infections. a bone marrow transplant from a healthy donor is the only
curative treatment for MDS.