Description Of The Four Types Of Leukemia Biology Essay

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Leukemia is a cancer of the blood that takes place in the bone marrow and involves abnormal uncontrolled cell growth. It can involve either the lymphocytes or myeloid cells which are two types of white blood cells. The four types of Leukemia are acute and chronic lymphocyitc (ALL, CLL) and myelogenous (AML, CML). Treatments of all forms of leukemia involve either chemotherapy, radiation or a combination of both and in some cases a bone marrow/stem cell transplant is required.

Description

Leukemia is a cancer of the blood which, like other forms of cancer, involves abnormal and uncontrolled cell division (umm.edu). Leukemia takes place in the bone marrow which is the soft flexible tissue in the center of the bone responsible for the body’s production of both red and white blood cells as well as platelets. It starts out a somatic mutation in a persons DNA causing abnormal (mutated) chromosomes. The marrows progenitor cells then begin to create an abnormal amount of white cells through mitosis (umm.edu). In some cases the cells are undeveloped stem cells and in other cases the cells develop abnormally (wikipedia.org). In both cases the rapidly dividing cells crowd the bone marrow, leaving less room and energy for the production of red cells, platelets and functional white cells. As a result many of the essential functions of the body are severely compromised. Due to the lack of functioning white blood cells the body looses its ability to fight infections. Decreased numbers of platelets affect the process of clotting leading to excessive bruising and bleeding. Low levels of red blood cells which are used to transport oxygen through the blood stream cause anemia all of which can be fatal.

Types

There are four main types of leukemia: acute lymphocytic leukemia (ALL), acute myelogenous leukemia (AML), chronic lymphocytic leukemia (CLL) and chronic myelogenous leukemia (CML). The difference between lymphocytic and myelogeneous leukemia is the type of white blood cell they affect. In cases of lymphocytic leukemia T and B cell lymphocytes are mutated. T and B cells in their normal state are responsible for recognizing foreign antigens and then producing antibodies to neutralize (T) and kill (B) pathogens (leukemia-lymphoma.org). In the long term these cells are what build up a persons immunities. In the case of myelogeneous leukemia granulocytes are affected. Granulocytes are normally responsible for the consumption and disposal of dead cells including pathogens as well as cellular debris (cancer.org). For this reason the balance between regenerated and dead cells is disrupted. Acute leukemia deals with the proliferation of immature cells (stem cells) while with chronic leukemia the cells are mature but damaged limiting their ability to perform their cellular level functions (ncbi.gov). Theses terms also refer to the rate of increase in their respected abnormal cells. In the case of acute leukemias cell division is very rapid often presenting symptoms shortly after development and requiring immediate treatment. With chronic leukemias on the other hand, cellular division occurs at a much slower rate, this can lead the patient being asymptomatic long after the development of the leukemia. One detail specific to chronic myelogenous leukemia is the characteristic genetic abnormality that involves part of chromosome 9 translocating to chromosome 22; this is referred to as the Philadelphia chromosome (mayoclinic.com).

Signs and Symptoms

Due to the significant similarities between the four major forms of leukemia, sings and symptoms are often the same requiring complete blood counts and bone marrow spicule evaluation to determine the type. People with leukemia show symptoms at different times depending on the type; those symptoms include:

Fever or chills

Persistent fatigue, weakness

Frequent infections

Losing weight without trying

Swollen lymph nodes, enlarged liver or spleen

Easy bleeding or bruising

Tiny red spots in your skin (petechiae)

Excessive sweating, especially at night

Bone pain or tenderness

Low white cell counts, especially monocytes or neutrophils. (mayoclinic.com)

Treatments

Upon diagnosis healthcare specialist must decide on a plan for treatment. Though the specifics of each individual protocol vary case by case, treatment typically involves chemotherapy, radiation or a combination of both. In some cases with a high risk of reoccurrence a bone marrow/stem cell transplant may be necessary of recommended for precautionary measures. There are a some cases where based on age and other health factors these treatments poses too high a risk; in these cases a quality over quantity of life approach is taken where treatment aims toward relieving the symptoms of the leukemia rather than cure.

Chemotherapy: With chemotherapy treatment patients are given antineoplastic drugs in order to kill cancerous cells (cancer.gov). These drugs however do not target only cancer cells instead they affect all rapidly dividing cells including healthy blood cells and other cells such as hair follicles (this is why a typical side effect of chemotherapy is hair loss). Chemotherapy drugs are typically given intravenously but can sometimes be administered orally.

Radiation: Radiation therapy involves the use of ionizing radiation in order to control the growth of malignant cells (wikipedia.org). Radiation therapy works by damaging the DNA of the cancerous cells causing regeneration to stop or slowdown and some times reduce in size (umm.edu). Therapy is typically targeted to the affected area (e.g. cranial, breast, prostate, etc) of the body due to its potentially harmful side effects.

Bone Marrow/Stem Cell Transplant: In some patients a stem cell transplant (formerly known as a bone marrow transplant) is necessary. During a transplant healthy stem cells are collected from the peripheral blood (previously they were taken from bone marrow) and then often treated with chemotherapy agents to gat rid of any leukemia cells still present (cancer.gov). The stem cells are then introduced or reintroduced in to the patient in order to restore the health of the bone marrow so that it can produce more healthy blood cells. Stem cell transplants can be either autologous (coming from the patient) or allergenic (coming from a donor). In the case of allergenic transplants donors must have well matched tissue type in order to reduce the risk of graft vs host disease where the host body recognizes the graft stem cells as being foreign resulting in the immune system attacking those cells (cancer.gov).

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