Acute lymphocytic leukemia: Description, Causes and Risk Factors:
Alternative Names: Acute lymphatic leukemia, acute lymphoblastic leukemia, acute lymphoid leukemia.
Def: A variety of leukemia characterized by an uncontrolled proliferation and conspicuous enlargement of lymphoid tissue in various sites (e.g., lymph nodes, spleen, bone marrow, lungs), and the occurrence of increased numbers of cells of the lymphocytic series in the circulating blood and in various tissues and organs; in chronic disease, the cells are adult lymphocytes, whereas conspicuous numbers of lymphoblasts are observed in the more acute syndromes.
Leukemia is the general name given to a group of cancers that develop in the bone marrow. Leukemia originates in developing blood cells, which have undergone a malignant change. This means they multiply in an uncontrolled way and do not mature as they are supposed to. Because they have not matured properly, these cells are unable to function properly. Most causes of leukemia originate in developing white cells. In small number of cases leukemia develops in other blood-forming cells, for example in developing red cells and developing platelets.
Types of leukemias include acute and chronic:
Acute leukemias develop and progress quickly and need to be treated as soon as they are diagnosed. Acute leukemias affect very immature blood cells, preventing them from maturing properly.
Chronic leukemias develop slowly, during the early stages of disease, and progress slowly over weeks or months. Chronic leukemias generally involve an accumulation of more mature but abnormal white cells.
Acute lymphocytic leukemia (ALL) is a fast-growing cancer of a type of white blood cells called lymphocyte (a white blood cell formed in lymphatic tissue throughout the body (e.g., lymph nodes, spleen, thymus, tonsils, Peyer patches, and sometimes in bone marrow) and in normal adults making up approximately 22-28% of the total number of leukocytes in the circulating blood. Lymphocytes are generally small (7-8 4m), but larger forms are frequent (10-20 ?m); with Wright (or a similar) stain, the nucleus is deeply colored (purple-blue), and is composed of dense aggregates of chromatin within a sharply defined nuclear membrane; the nucleus is usually round, but may be slightly indented, and is eccentrically situated within a relatively small amount of light blue cytoplasm that ordinarily contains no granules; especially in larger forms, the cytoplasm may be fairly abundant and include several bright red-violet fine granules; in contrast to granules of the myeloid series of cells, those in lymphocytes do not yield a positive oxidase or peroxidase reaction. Lymphocytes are divided into 2 principal groups, termed T and B cells, based on their surface molecules as well as function. Natural killer cells, which are large granular lymphocytes, represent a small percentage of the lymphocyte population).
In most cases, the leukemia invades the blood fairly quickly. It can then spread to other parts of the body, including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles (in males). Other types of cancer that start in these organs and then spread to the bone marrow are not leukemia.
ALL occurs in people of all ages but is the most common cancer in children, accounting for 25% of all cancers in children younger than 15 years.
Causes and Risk Factors:
Genetic Translocation: The most common genetic translocation in acute lymphocytic leukemia is the Philadelphia (Ph) chromosome where DNA is swapped between chromosomes 9 and 22 [t(9:22)]. It occurs in about 20 - 30% of adults and 3 - 5% of children with acute lymphocytic leukemia. Another common translocation in acute lymphocytic leukemia is t(12;21), which is referred to as TEL-AML1 fusion. It occurs in about 20% of patients with acute lymphocytic leukemia. Researchers believe that this translocation may occur during fetal development in some patients.
Radiation: People exposed to large doses of radiation are more likely to develop acute lymphocytic leukemia. People who have received large doses of radiation therapy for the treatment of cancers also have an increased risk of developing acute lymphocytic leukemia.
Chemicals: Exposures to high level of benzene over a long period of time may increases the risk of some blood disorder like acute lymphocytic leukemia.
Certain viral infections: Infection with the human T-cell lymphoma/leukemia virus-1 (HTLV-1) can cause a rare type of T-cell acute lymphocytic leukemia. Most cases occur in Japan and the Caribbean area. This disease is not common in the United States. Epstein-Barr virus (EBV) most often causes infectious mononucleosis ("mono") in the United States. In Africa, the virus has been linked to Burkitt lymphoma, as well as to a form of acute lymphocytic leukemia.
Certain disease or conditions: Down syndrome, Klinefelter syndrome, Fanconi anemia, Bloom syndrome, ataxia-telangiectasia, neurofibromatosis.
Other factors that have been studied for a possible link to acute lymphocytic leukemia include: Exposure to electromagnetic fields (such as living near power lines), Workplace exposure to diesel, gasoline, pesticides, and certain other chemicals, smoking, exposure to hair dyes.
Patients with acute lymphocytic leukemia often have several non-specific symptoms. These can include weight loss, fever, night sweats, fatigue, and loss of appetite. Of course, these are not just symptoms of acute lymphocytic leukemia and are more often caused by something other than leukemia.
Symptoms may include:
Bone and joint pain.
Easy bruising and bleeding (such as bleeding gums, skin bleeding, nosebleeds, abnormal periods).
Swollen glands (lymphadenopathy) in the neck, under arms, and groin.
If any signs and symptoms suggest the possibility of leukemia, the doctor will want to get a thorough medical history, including how long you have had symptoms and if you have any history of exposure to risk factors.
During the physical exam, the doctor will probably focus on any enlarged lymph nodes, areas of bleeding or bruising, or possible signs of infection. The eyes, mouth, and skin will be looked at carefully, and a thorough nervous system exam will be done. Your abdomen will be felt for signs of an enlarged spleen or liver.
If there is reason to think the problems might be caused by abnormal numbers of blood cells (anemia, infections, bleeding or bruising, etc.), the doctor will probably test your blood counts. If the results suggest leukemia may be the cause, the doctor may refer you to a oncologist, who may run one or more of the tests described below.
Tests may include:
Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia. Patients suffering from acute lymphocytic leukemia may have high leukocyte counts and typically have low counts of both red blood cells and platelets. Many patients with ALL have low counts of all of the major components of the blood.
A microscopic exploration of the blood will usually show that leukemic blast cells are present. However, the diagnosis has to be confirmed by more specific tests.
The doctor may also perform a bone marrow aspiration and biopsy to confirm the diagnosis of ALL. Aspiration involves the withdrawal of a liquid sample of marrow. During the biopsy, a cylindrical piece of bone and marrow is removed. The tissue is generally taken out of the hipbone. These samples are sent to the laboratory for examination.
Lumbar puncture (spinal tap) to check for leukemia cells in the spinal fluid.
Cytogenetic studies, which examine the number and shape of the chromosomes in the DNA (deoxyribonucleic acid) of individual blast cells, should be conducted in addition to the immunophenotyping of cells of the bone marrow. This procedure involves applying various stains to the marrow cells. These stains help doctors identify some of the proteins lying on the surface of the cells.
Fluorescent in situ hybridization (FISH): This is another type of chromosome test. It uses special fluorescent dyes that only attach to specific parts of particular chromosomes. FISH can find most chromosome changes (such as translocations) that are visible under a microscope in standard cytogenetic tests, as well as some changes too small to be seen with usual cytogenetic testing. FISH can be used to look for specific changes in chromosomes. It can be used on regular blood or bone marrow samples. It is very accurate and can usually provide results within a couple of days.
Polymerase chain reaction (PCR): This is a very sensitive DNA test that can also find some chromosome changes too small to be seen with a microscope, even if very few leukemia cells are present in a sample. These tests may also be used after treatment to try to find small numbers of leukemia cells that may not be visible with a microscope.
Imaging: Standard imaging tests such as x rays may be used to check whether the leukemic cells have invaded other areas of the body, such as the bones, chest, kidneys, abdomen, or brain. Other tests, such as CT scans (computed tomography scans), MIR (magnetic resonance imaging), or gallium scans, are not typical for myelocytic leukemia may also be performed.
The treatment of ALL varies according to one's age, general condition at diagnosis and the results of the cytogenetic testing. Standard therapy for ALL has changed very little in the last 15 years or so, as the current strategy has been very effective at curing adults. The goal of treatment is a cure. Treatment can be divided into four phases:
First phase — Induction chemotherapy.
Second phase — Consolidation chemotherapy.
Third phase — Maintenance chemotherapy.
Fourth phase — Central nervous system (CNS) prophylaxis.
Chemotherapy is the primary treatment for each stage. Radiation to the brain and spinal cord is also administered in some cases. New drugs known as biological therapies are also being used.
For some patients, a bone marrow or cord blood transplant may offer the best chance for a long-term remission. A transplant is a strong treatment with risks of serious side effects, so it is not used for all patients with ALL. A transplant is used when chemotherapy alone is unlikely to provide a long-term remission.
Types of transplants:
Autologous transplant: An autologous transplant uses blood-forming cells collected from the patient. If an autologous transplant is a treatment option for you, you will have blood-forming cells collected from your blood stream. The cells are usually collected after one or two cycles of consolidation treatment. The cells are frozen until you are ready for transplant. You may receive an autologous transplant soon after your induction therapy is completed, or your cells may be saved as a backup option in case you relapse after receiving consolidation chemotherapy.
Allogeneic transplant: An allogeneic transplant replaces the abnormal cells in a patient's bone marrow with healthy blood-forming cells from a family member or unrelated donor or cord blood unit. An allogeneic transplant has a higher risk of serious side effects than consolidation chemotherapy or an autologous transplant. However, the risk of relapse is lower after an allogeneic transplant.
Side effects of treatment usually present.
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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