Publié par happy-diet vendredi 14 mai 2010

Noun: Myelodysplasia is a diagnosis that includes several subcategories with very different findings and different prognoses . The common element in all of the myelodysplasias is anaemia, usually refractory , meaning that treatments other than blood transfusions are often not helpful. Bone marrow transplants may lead to long-term disease-free survival, but the majority of patients with MDS are over the age of 50 and too old to be eligible for a BMT .

Blood cells must be mature to carry out their specific work properly. In the myelodysplastic syndromes, the blood cells lose their ability to mature. Under a microscope, the red and white cells show that they have not matured normally. There may also be an increase in the number of these immature blood cells (called blasts). As the disease progresses, the blasts take over the bone marrow and prevent it from making enough of the normal red blood cells , white blood cells and platelets that the body needs. The mature blood cells that are present may not work properly. Myelodysplastic syndromes are divided into several types based on how the bone marrow cells and blood cells look under a microscope. There are five types of myelodysplastic syndromes. Each type is defined according to the type and percentage of immature blood cells (blasts) found in the blood stream and bone marrow.

The five types are:

Refractory anaemia (RA)

(less than 5 percent blasts in bone marrow)

Refractory anaemia with ringed sideroblasts (RARS)

(less than 15 percent blasts in the bone marrow)

The picture below is from a patient with RARS. The larger cells are immature red blood cells with a nucleus.

On the right is an iron stain in the same patient showing rings of iron around the nucleus of the immature red cells.

Refractory anaemia with excess blasts (RAEB)

(5-20 percent blasts) The picture below is from a patient with RAEB

Refractory anaemia with excess blasts in transformation (RAEB-t)

(21-30 percent blasts)

Chronic Myelomonocytic Leukaemia (CMML)

(5-2O percent blasts)

The syndromes that primarily affect the red cells are refractory anaemias (RA) and refractory anaemias with ringed sideroblasts (RARS). In RA, the developing red cells in the bone marrow are unable to process the iron that normally goes into the haemoglobin . In cases of RARS, the iron may be deposited inside the red cell to form a characteristic ring that can be seen under the microscope. These two forms of anaemia, RA and RARS, are the most common forms of MDS . These forms of MDS rarely progress to acute leukaemia .

When MDS predominantly affects the white cells, blasts appear in the bone marrow in abnormally large numbers. It is normal to have a small number of blasts (less than 5 percent) in the marrow, but this number may increase to over 35 percent in MDS patients. This form of MDS is called "refractory anaemia with excess blasts" or RAEB. About 40% of patients with RAEB will eventually develop acute leukaemia.

If the blasts become especially numerous this may indicate a chance of transformation to acute myelogenous leukaemia. This condition is called "refractory anaemia with excess blasts in transformation" or RAEB-t. This carries a 60 to 70% chance of becoming leukaemia.

Chronic myelomonocytic leukaemia (CMML) is usually classified as a form of MDS. The hallmark of CMML is an increase in the type of white cell called a monocyte . Normally, monocytes circulate throughout the body as a defence against some bacteria infections such as tuberculosis. Since monocytes are among the most mature white cells produced in the bone marrow, CMML can be a slowly progressing disease. In some cases it does progress rapidly, however, and can reach an acute leukemic stage.

Myelodysplasia is generally a disease of the elderly, and may also be seen after chemotherapy for cancer. It is thought to be due to a mutation in one of the genes of the stem cell, leading to an overgrowth of one type of cell and suppression of the other cells that normally derive from the stem cell. As one might expect, the overgrowth of one type of cell often develops into leukaemia, which is a cancer of a bone marrow cell type.

Because the anaemia in myelodysplasia cannot usually be treated, except by bone marrow transplant, it is often necessary to give people with this condition repeated blood transfusions. As with other anaemias requiring frequent transfusions, this can occasionally lead to haemosiderosis , a condition where too much iron builds up in the body. Treatments using various growth factors that have been developed during the past ten years or so are under investigation, and these may be promising. Bone marrow transplantation has cured the condition in many cases.

People with myelodysplasia often develop infections due to inadequate production of functional white blood cells, or severe bleeding due to inadequate production of platelets. These are the most common causes of death in this disease. If one has too many white cells taking over, this may mean that he has one of the subcategories of the disease characterised by excessive white cell precursors, which have a higher likelihood of developing into leukaemia. The large numbers of white blood cells produced in this subcategory of the disease do not function well to fight infection, so infection remains a serious complication.

MDS Symptoms

A diagnosis of MDS may be made during a regular check-up or routine blood tests. Many patients with MDS will go to see their doctor because they feel symptoms of anaemia. Anaemia means there are too few red blood cells to carry oxygen to the body, causing patients to feel tired (fatigue) and short of breath. Weakness and pallor are common signs of the diseases.

CMML patients may have other signs of the disease. Their lymph glands or spleen may enlarge.

For many patients, there may be too few white cells to fight infections. They might get infections more easily. Patients may have infections that do not get better after taking antibiotics.

A shortage of platelets is commonly found in MDS patients. These patients experience bruising or abnormal bleeding from a small injury (i.e., cut finger) or minor surgical procedure (i.e., tooth extraction).

Patients should report these symptoms to their doctor so that the status of the MDS can be determined, and treatment started to relieve many of these symptoms. Patients will then begin to feel more comfortable.

Preventive Measures

There are measures patients with low white blood cell counts can take to limit the risk of developing an infection. See Clean Diet and Program 2: Increase Hygiene

  • Avoid exposure to crowds or to people with colds or contagious diseases.
  • Practice good hygiene, including frequent hand washing.
  • Make a practice of taking your temperature if you are having a poorer day than normal. The reason might be due to some internal infection. Your body will tell you by raising it's temperature above 37.5°C in an effort to handle it. Contact your doctor if it is above 37.5°C , certainly if it is above 38°C.
  • Brush teeth regularly, bathe or shower daily; and pay special attention to hard-to-clean areas such as skin folds and the rectal area.
  • Avoid cuts and scrapes. Patients with MDS who think they might get injured while at work or engaging in hobbies or sports activities, should ask their health care provider about ways to protect themselves.
  • If you notice some infection such a cut that is inflamed, gum or tooth infection, or your temperature goes high (37.5° C +) report this to your doctor ASAP so he can evaluate your situation and give you the correct antibiotics if needed.
  • If your neutrophil count is less than .3 (some doctors have said .5) you should be in an isolation ward when you are in the hospital. Therefore it makes sense that when you leave the hospital and go home you should treat your home as an isolation ward as well. The soil and plants inside your house and outside are a source of the fungus aspergillus which grows in decaying vegetation. Get rid of plants and fresh flowers in your house and limit your time outside as the aspergillus spores are usually present in the air all year round.
  • Showers should be run hot for at least 5 minutes each week if not normally used to eliminate bacterial growth in them and grouting around shower kept clean to prevent mould.
  • Kitchen and bathroom sinks and bath tubs should be cleaned with soap and water or a disinfectant and dried thoroughly after each use.
  • Use liquid soap in the bathroom. The bars of soap often remain wet and are a breeding place for dangerous bacteria.

Some infections can be prevented and almost all infections can be treated. People with MDS should be a full partner with the health care team by taking care of themselves and reporting any problems they may have.

Low Platelet Count

Another type of blood cell affected by the myelodysplastic syndromes is the platelet. Platelets help the blood to clot. If platelets are deficient, patients may develop bruises, may bleed easier than usual, or have trouble stopping the bleeding. For example, patients might notice blood on their toothbrush from bleeding gums or might develop nosebleeds. Women may experience heavy menstrual periods. Some people get tiny, red spots on their skin, especially on the arms or legs. These are called petechiae . Blood in the urine and stool sometimes occurs.

Symptoms and Treatment

Symptoms you should report to your doctor or hospital immediately include:

  • Unusually heavy or prolonged bleeding anywhere
  • Severe headache or visual changes
  • Stiff neck

Physicians may order a platelet transfusion when the platelet count is low or to prevent or stop excessive bleeding. For this treatment, platelets usually are given through a needle inserted into a vein. Patients receive transfusions during an outpatient visit to the hospital, usually lasting several hours.

Preventive Measures

Safety measures to take include.

  • Avoid activities that can result in bruising or bumping.
  • Put off the use of sharp instruments such as tools, nail trimmers, razors or knives.
  • Wear hard-sole shoes, gloves, or thick pants.
  • Ask health care providers about the use of special sponge toothbrushes for people who have problems with gum bleeding. Use them if it is recommended.
  • Some medications can affect clotting ability. It is important to avoid medications that contain aspirin or aspirin-like products (for example, Motrin, ibuprofen, or other anti-inflammatory drugs) unless the doctor has instructed otherwise as these reduce platelet count. Ibruprofen and others may also cause bleeding in the stomach which can be serious if your platelet levels are very low.
  • Remember to report any signs that platelet counts might be low, such as easy bruising, nose or gum bleeding, blood in urine or petechiae (tiny red spots on arms or legs).

Low Red Blood Cell Count

The red blood cells carry oxygen to all parts of the body. The myelodysplastic syndromes may cause the number of red blood cells to go down. This condition is called anaemia.

Symptoms and Treatment

Without enough oxygen, patients may feel short of breath or feel their heart is pounding very fast. As a result, people with MDS may feel tired and look pale. If these side effects are severe, inform your doctor right away. Transfusions of red blood cells may be prescribed to help these symptoms. Red cell transfusions are matched by blood types. First, a sample of the patient's blood is sent to the blood bank to identify its types: A, B, O, AB. Each type is either Rh positive or negative. This is called "typing the blood." A small sample of the donor blood is then matched to the blood type. A transfusion of only red blood cells, called a "unit" of packed RBCs (red blood cells), is given to the patient through a needle in the arm. Transfused blood should be leucocyte depleted and irradiated.

Preventative Measures

  • A well-balanced diet is important to combat anaemia. This helps the body to make new red blood cells.
  • It may be beneficial to sleep more and rest between activities so the body can conserve energy.
  • Light exercise such as walking may give patients more energy.
  • Spend energy on accomplishing important tasks.

MDS patients who need dental work should discuss this with their doctor or nurse. Infection and/or bleeding could be problems if dental work is done when blood counts are low. Patients may be given medications between treatments to help stimulate the production of blood cells. Health care providers will discuss these medications if they are prescribed.

Patients with MDS should inform their doctor or dentist of the condition when they seek treatment for dental or other medical circumstances.

Acute Myelogenous Leukaemia

Sometimes the myelodysplastic syndromes transform or change from a preleukaemic state to acute myelogenous leukaemia (AML). AML involves immature white blood cells produced in large numbers by the bone marrow (blasts >30 percent). Patients whose disease does transform to AML will be offered treatments for this form of leukaemia.

Chemotherapy is the most common method of treatment. Various antileukaemic drugs are used, either in combinations or as single agents. Once the disease undergoes acute leukemic transformation, prognosis is related to responsiveness to chemotherapy (which is usually somewhat lower for transformed MDS than for other types of AML).

Transformation to acute leukaemia occurs in only a minority of cases. The possibility of this transformation occurring varies according to the type of MDS. A slightly higher risk is present in cases of refractory anaemia with excess blasts (RAEB) and chronic myelomonocytic leukaemia (CMML).

Greek - myelós = marrow +
Greek - dys = bad +
Greek - plassein = to form

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