Myelodysplastic syndromes, known also as myelodysplasia, are a group of disorders characterized by malfunctioning stem cells in the bone marrow, leading to a decreased amount of healthy blood cells. This in turn can lead to several complications and health problems. Unfortunately, there is no cure, and treatment is focused on managing the symptoms and a variety of therapies. The method of treatment used is dependent on the how the condition occurred.
Types, Causes and Symptoms
The World Health Organization has divided myelodysplastic syndromes into eight subtypes, with each one containing unique blood cell and bone marrow characteristics. They include: refractory anemia, refractory anemia with ringed sideroblasts, refractory cytopenia with multilineage dysplasia, refractory cytopenia with multilineage dysplasia and ringed sideroblasts, unclassified myelodysplastic syndrome, refractory anemia with excess blasts types 1 and 2 and myelodysplastic syndrome associated with isolated del(5q) chromosome abnormality.
The exact cause of myelodysplastic syndromes is unknown. Most cases are idiopathic (arising spontaneously with no known cause) and are known as de novo myelodysplastic sydnromes. These are typically easier to treat than secondary myelodyspastic syndromes, which usually occur after treatment for cancer or long-term exposure to a variety of environmental toxins such as heavy metal and pesticides.
Symptoms typically begin to appear as the supply of healthy blood cells begin to dwindle. They can include fatigue, pale skin, bleeding underneath the skin, weight loss and infections.
The main side effect of myelodysplastic syndrome is a lack of red blood cells, called anemia. This can often lead to fatigue. To treat this transfusions of red blood cells may be given. The procedure is typically safe with no limit as to how many times it can be performed. In the event that platelets are significantly reduced, they can be transfused as well.
Possible side effects include the possibility of antibodies developing to the transfused blood cells, which can weaken their impact. In addition, the red blood cells contain iron, which can accumulate and cause potentially serious heart and liver problems. This is typically offset with doses of vitamin C and a chelating (binding) agent such as deferasirox administered intravenously, which decreases the iron’s toxicity.
Medications known as hematopoietic (literally “blood makers”) growth factors exist to help replenish lost red blood cells by increasing their production. Examples include erythropoietin and darbepoetin. Other growth factors can increase the supply of white blood cells, which can strengthen the immune system and help fight off infections.
Two drugs have been approved by the Food and Drug Administration for treating myelodysplastic syndromes: azacitidine and decitabine. Known as differentiation agents, they work by encouraging blast cells (cells in the maturation stage) to properly develop into healthy red blood cells. These drugs are effective in that they may slow down or prevent the progression of the condition into acute myelogenous leukemia.
Finally, lenalidomide, a drug with a chemical makeup similar to thalidomide, can be used in patients with myeloplasia associated with isolated del(5q) chromosome abnormality. Its effectiveness can do away with the need for blood transfusions, and side effects are minimal. A study published in the February 2005 New England Journal of Medicine concluded that lenalidomide was an effective method of treatment for those who did not respond to erythropoietin (a protein that produces red blood cells) or were unresponsive to conventional therapy.
Stem Cell Transplant
Stem cell transplants are one of the most effective ways to treat myelodysplastic syndromes, though they also possess the highest risks, especially for older adults. Transplant-related deaths are common, and as such, most are not suited for the transplant.
A new form of stem cell transplant designed to be more effective and less dangerous in adults is nonmyeloablative transplantation. Before a stem cell transplant, host stem cells are typically destroyed through chemotherapy before the implantation of donor ones. Given the potential for stem cell transplants to be rejected, nonmyeloablative transplantation involves suppression of the immune system to prevent this from happening, avoiding the need for high doses of chemotherapy.