Leukemia is the most common disease of blood and bone marrow cancer. Cancer builds up in the body when any mutation or change occurs in the normal cells and results in the uncontrolled growth of cancerous cells. Leukemia starts developing from bone marrow tissues and results in the uncontrollable growth of abnormal blood cells. Bone marrow is the spongy tissue that is found in the center of bones and is responsible to produce all three types of blood cells for the whole body. These blood cells include red blood cells (which carry oxygen and nutrient material to the whole body), white blood cells (which fight infections), and platelets (which help in blood clotting). 
Billions of fresh and new blood cells are produced by bone marrow every day. In normal body conditions, the amount of red blood cells is larger than white blood cells and platelets. Since the leukemia cells are cancerous white blood cells, leukemia comes from the Greek word leukos (white) and haima (blood). In leukemia, the abnormal growth of white blood cells starts and these cancerous white cells spill into other blood cells and create an imbalance in normal blood count. Yet these leukemia cells may also form cells other than white blood cells as well but their chances are rare. These cancerous cells affect the body in various ways:
- The leukemia cells do not serve any useful purpose to the body.
- In presence of luekemia cells, normal blood cells do not get space and any support to grow in the bone marrow.
As a result, the amount of cancerous white blood cells increases, they begin to affect the normal functioning of the body. These cancerous white cells don’t tend to fight against infections than normal white cells. Over time, the growth of leukemia cells reaches such an extent where the body does not have enough normal white cells that can fight infection or does not have enough red cells that can carry oxygen to the body’s organs, or does not have enough platelets that can clot blood.
Consequently, there comes a time when leukemia cells begin to affect the other organs of the body like the central nervous system, lymph nodes, spleen, and liver.
Leukemia exists in different types. Some types of leukemia occur in children and some types occur in adults. However, it is diagnosed most frequently in people from age of 65 to 74 years. Leukemia mostly affects men than women and affects Caucasians than African-Americans. According to the latest statistics, leukemia is the 10th most common type of cancer found in the world. In the United States, About 14 leukemia’ cases are found each year in every 100,000 women and men. Leukemia is different from other cancer in a way that it does not form any kind of tumor in the body and can’t be diagnosed through X-ray. The symptoms of leukemia are attributed to other diseases therefore leukemia is diagnosed with a microscopic blood test. Since leukemia of each type is not easy to treat and its symptoms and treatment vary according to its type. The symptoms, causes, treatment, and various types of leukemia are described in the following:
1Types of Leukemia
Classification according to speed
Leukemia is classified based on the time (that of how long the disease gets worsen) into two types.
- Acute leukemia
It is most common in children where cancerous cells start to grow and divide rapidly. Its symptoms appear within a few weeks.
- Chronic leukemia
Chronic leukemia mostly occurs in adults. This disease develops slowly than acute leukemia and the patient does not notice any symptoms for months or even years.