Description, Causes and Risk Factors:
Alternative Name: Preleukemia, bone marrow failure disorder.
The bone marrow functions as a factory that manufactures three kinds of blood cells: RBCs (red blood cells), WBCs (white blood cells), and platelets. Healthy bone marrow produces immature blood cells - called stem cells, progenitor cells, or blasts - that normally develop into mature, fully functional blood cells, white blood cells, or platelets. In MDS, these stem cells may not mature and may accumulate in the bone marrow or they may have a shortened lifespan, resulting in a fewer than normal mature blood cells in the circulation.
Myelodysplastic syndromes (MDS) are a complex and heterogeneous group of bone marrow failure disorders characterized by ineffective hematopoiesis. This dysfunctional blood cell production is manifest by peripheral cytopenias, marked morphologic dysplasia, and cellular dysfunction resulting in an increased risk of infection and need for transfusions in most MDS patients. There are 7 categories of MDS in the WHO system:
Refractory anemia with ringed sideroblasts (RARS).
Refractory cytopenia with multilineage dysplasia (RCMD).
Refractory anemia with excess blasts-1 (RAEB-1).
Refractory anemia with excess blasts-2 (RAEB-2).
Myelodysplastic syndrome, unclassified (MDS-U).
Myelodysplastic syndrome associated with isolated del(5q).
Refractory cytopenia with unilineage dysplasia (RCUD).
The cause of MDS is unknown, but research shows that certain risk factors are associated with the disease.
People with certain inherited syndromes are more likely to develop myelodysplastic syndrome. These disorders include Fanconi anemia, Shwachman-Diamond syndrome, familial platelet disorder, and severe congenital neutropenia.
People who have received previous chemotherapy or radiation treatment for cancer have an increased risk of developing MDS, because chemotherapeutic agents and radiation therapy can cause damage to the stem cells in the bone marrow. When chemotherapeutic drugs are combined with radiation therapy, a patient's level of risk of developing MDS and leukemia is heightened.
Environmental risk factors, such as radiation and certain chemicals, have been linked to myelodysplastic syndrome. High-dose radiation exposure (such as surviving an atomic bomb blast or nuclear reactor accident) increases the risk of developing myelodysplastic syndrome. Long-term workplace exposure to benzene and certain chemicals used in the petroleum and rubber industries can also increase the risk of developing myelodysplastic syndrome.
Smoking increases the risk of myelodysplastic syndrome. Many people know that smoking can cause cancers of the lungs, mouth, throat, larynx, and other organs, but few realize that it can also affect areas that do not come into direct contact with smoke. Cancer-causing substances in tobacco smoke are absorbed into the blood as it passes through the lungs. Once in the bloodstream, these substances spread to many parts of the body.
In the US, myelodysplastic syndrome occurs at a rate of 4.4 cases for every 100,000 people. That works out to about 12,000 new cases of myelodysplastic syndrome each year. The number of new cases diagnosed each year seems to be increasing as the average age of the population has increased.
About 80% to 90% of all patients with myelodysplastic syndrome are older than 60 years. It is rare in young adults.
Signs and symptoms may include:
Shortness of breath.
Loss of appetite.
Bone and joint pain.
Bleeding that does not stop easily.
Tiny red lesions (most common on your ankles, chest, and roof of mouth).
Blood in your urine or stool.
Myelodysplastic syndromes can be difficult to diagnose. Several other diseases closely resemble this syndrome and can be confused with MDS. Accurate diagnosis of MDS-associateddysplasia requires a review of the peripheral blood smearas well as a bone marrow aspirate and biopsy. Morphological analysis is performed to determine the percentageof myeloblasts; it is also performed because specific cytological abnormalities can be found in the blood and bonemarrow.Peripheral blood smears may reveal hypogranulated neutrophils with hyposegmented nuclei and large platelets, whilebone marrow dysplasia affects the erythroid, myeloid, ormegakaryocytic lineages.
Tests may include:
Bone marrow tests: Biopsy test is done on a small piece of bone and marrow and is required to confirm the MDS sub-type. Aspiration test is done on a small amount of liquid bone marrow and is required to confirm low counts of blasts inside the marrow.
Blood tests: Complete blood count (or CBC) and blood smear. Myelodysplastic syndrome is usually characterized by having too few blood cells (red blood cells, white blood cells, and platelets) and having abnormalities in size, shape, and other features in the appearance of blood cells.
Tests that are performed on bone marrow samples include:
Histochemistry studies: Physicians look at the bone marrow cells to see if the cells look abnormal (or dysplastic). With these tests, the bone marrow blast count can also be determined, and the pathologist can look for other causes of bone marrow malfunction.
Flow cytometry: Cells are passed through a laser beam for analysis to see if the bone marrow cells are developing normally and to obtain an estimate of the blast count.
Molecular genetic studies: Highly sensitive DNA and RNA tests are done to determine the specific genetic traits of the bone marrow cells.
Cytogenetic studies: These studies help to determine chromosome changes in bone marrow cells. Each cell in the body contains chromosomes (46 tightly coiled strands of DNA). Chromosomes contain all the information that cells need to function normally. In about half of patients with MDS, one or more chromosomal changes can be identified. The most common abnormalities are seen in chromosomes 5, 7, 8, and 20.
Myelodysplastic syndrome is not just one disease; it is a group of related diseases. The different types of myelodysplastic syndrome vary in their prognosis and response to treatment. Treatment is based on the type of myelodysplastic syndrome, as well as the patient's age and health. Patients with these diseases are treated by specialists, such as a hematologist or an oncologist.
Different treatment options for MDS are listed below.
Drug therapy: Some drug therapies may increase healthy cell growth and decrease abnormal cell growth. Other drug therapies may help prevent the body's immune system from attacking bone marrow cells.
Supportive care, which include the use of red blood cell transfusions to manage the symptoms of anemia and iron chelation therapy to manage iron overload, platelet transfusions for thrombocytopenia, and antibiotics to fight persistent or recurrent infections.
Myeloid growth factors like erythropoietin to stimulate healthy blasts in the bone marrow to produce red and white blood cells as well as platelets.
Bone marrow transplant: In bone marrow transplants, healthy marrow replaces unhealthy marrow. Bone marrow transplants for MDS are rare. They are more often done in people younger than 60 years old because of the risks and stress they can put on the body.
Stem cell transplant: As in a bone marrow transplant, healthy stem cells replace unhealthy stem cells. Stem cell transplants are usually done in people younger than 50 years of age.
Researchers are continually testing new treatments for MDS, and many of these investigational approaches are offered to eligible patients here through the clinical trial process, which is designed to advance the current standard of care for MDS.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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