What Is Leukemia?

Leukemia

By: Carla Aboumatar

[pic 1]

Table of Contents

What is Leukemia?

In general cancer is a disease caused by an uncontrolled division of abnormal cells in a part of the body. Leukemia specifically is a type of cancer that starts in blood stem cells. Stem cells are basic cells that develop into different types of cells that have different jobs. Blood stem cells can develop into two types of stem cells, lymphoid stem cells or myeloid stem cells. Lymphoid stem cells develop into lymphocytes which is a type of white blood cell that assists in fighting infection and destroying abnormal cells. There are three types of lymphocytes called B cells, T cells and natural killer cells. Myeloid on the other hand is a stem cell that develops into red blood cells, granulocytes, monocytes or platelets. The role of red blood cells is to carry oxygen to all tissues of the body. Granulocytes and monocytes are types of white blood cells that destroy bacteria and help fight infection and platelets circulate in the blood stream to carry out their proper function by clotting blood vessel injuries to stop the bleeding.

As the stem cells of the blood develop they become blood cells called blast cells. However, in leukemia there is an overproduction of blast cells and they do not develop into mature blood cells instead they develop abnormally and over time they crowd out normal blood cells so that the normal blood cells cannot carry out their proper functions. There are many different types of leukemia and these different types are grouped based on the type of blood stem cells that they have developed from and on how quickly the leukemia develops and grows. The 4 main types of leukemia are acute lymphocytic leukemia, acute myelogenous leukemia, chronic lymphocytic leukemia and chronic myelogenous leukemia.

The following diagram shows the development of blood cells: [pic 2]

The following diagram shows the difference beteewn normal blood cells and leukemia blood cells:

[pic 3]

What are the causes?

        Leukemia occurs when blood cells acquire mutations in their DNA. Certain abnormalities cause the cells to grow and divide more rapidly than usual and it also causes them to continue living when normal cells would die. These abnormal cells over time crowd out healthy blood cells in the bone marrow which leads to fewer healthy white blood cells, red blood cells and platelets leading to leukemia. Although what is happening on a cellular level is known the exact cause of leukemia is yet to be discovered however based on current research it is known to develop from a combination of genetic and environmental factors. Some genetic factors that could cause leukemia are genetic mutations. Genes are found in the DNA in each cell that makes up the human body and they control how the cells function. Genes do this by making proteins that have specific functions and act as messengers for the cell. Leukemia along with all other types of cancer begins when one or more genes in a cell are mutated. This creates either an abnormal protein or no protein at all. An abnormal protein provides different information than a normal protein would which causes the cells to multiply uncontrollably and become cancerous. There are two basic types of genetic mutations called acquired mutations and germline mutations. Acquired mutations are the most common cause of cancer. They occur from damaged genes and they cannot be passed from a parent to a child. Tobacco, ultraviolet radiation, viruses, and age are all factors that cause these mutations. Germline mutations on the other hand are less common causes of cancer. They are passed directly from a parent to a child since this mutation can be found in every cell of a person’s body including the reproductive sperm cells in a male’s body and egg cells in a female’s body and because the mutation affects reproductive cells it passes from generation to generation.  Some environmental factors that can cause leukemia include high doses of ionizing radiation or long term exposure to benzene.

Who is at risk?

The current factors known to increase the risk of developing leukemia are people who have high doses of radiation such as an exposure to atomic bomb blasts or nuclear accidents, people who have had radiation therapy, chemotherapy or a combination of both in the past given to treat cancer or other health conditions, exposure to benzene or formaldehyde, and genetic syndromes such as down syndrome, fanconi anemia, ataxia-telangiectasia and bloom syndrome. There might be other factors than these that cause people to be at risk however they have not been discovered.

Signs and Symptoms

General symptoms of leukemia include: fever, chill, fatigue, weakness, loss of appetite, weight loss, night sweats, bone or joint pain, abdominal discomfort, headaches, shortness of breath, frequent infections, easy bruising or bleeding and petechiae which is small red spots under the skin. Since some conditions correspondent with leukemia, having the following diseases may also be symptoms: Anemia which is when there is a low red blood cell count in the body. The function of red blood cells is to carry oxygen around the body and so this condition may contribute one of the common factors of leukemia being weakness, fatigue or shortness of breath. Leukopenia is a condition in which the body is low in white blood cell count. A decrease in the production of functional leukocytes weakens the body's immune defense which makes the body more prone to infections. Thrombocytopenia is when there is a low amount of blood platelets in the body. Platelets are the blood cells responsible for blood clotting and a shortage of bloods platelets may lead to easy bruising or bleeding. In some cases swollen lymph nodes may include noticeable swelling of the neck, armpit or groin and this occurs when leukemia has spread to the lymph nodes. An enlarged liver or spleen this is when there is a buildup of abnormal blood cells in the liver or spleen. This may cause a loss of appetite or swelling in the upper left side of the abdomen. The condition most likely to cause leukemia is myelodysplastic syndrome. This is a condition in which the bone marrow does not produce enough normal blood cells for the body and so this can progress to leukemia and more specificly acute myeloid leukemia.