Leukemia

Blood cells form in the bone marrow. Bone marrow is the soft material in the center of most bones.

Immature blood cells are called stem cells and blasts. Most blood cells mature in the bone marrow and then move into the blood vessels. Blood flowing through the blood vessels and heart is called the peripheral blood.

The bone marrow makes different types of blood cells. Each type has a special function:

-              White blood cells help fight infection. 

-              Red blood cells carry oxygen to tissues throughout the body.

-              Platelets help form blood clots that control bleeding.

Leukemia is the cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of blood cells to be produced and enter the bloodstream.

In people with leukemia, the bone marrow produces abnormal white blood cells. The abnormal cells are leukemia cells. At first, leukemia cells function almost normally. In time, they may crowd out normal white blood cells, red blood cells, and platelets. This makes it hard for blood to do its work.

The types of leukemia are grouped by how quickly the disease develops and gets worse. Leukemia is either chronic (gets worse slowly) or acute (gets worse quickly).

Chronic leukemia—Early in the disease, the abnormal blood cells can still do their work, and people with chronic leukemia may not have any symptoms. Slowly, chronic leukemia gets worse. It causes symptoms as the number of leukemia cells in the blood rises.

Acute leukemia—The blood cells are very abnormal. They cannot carry out their normal work. The number of abnormal cells increases rapidly. Acute leukemia worsens quickly.

 The types of leukemia are also grouped by the type of white blood cell that is affected. Leukemia can arise in lymphoid cells or myeloid cells. Leukemia that affects lymphoid cells is called lymphocytic leukemia. Leukemia that affects myeloid cells is called myeloid leukemia.

There are four common types of leukemia.

1. Chronic lymphocytic leukemia. Most often, people diagnosed with the disease are over age 55. It almost never affects children.

2. Chronic myeloid leukemia. It affects mainly adults.

3. Acute lymphocytic leukemia. It is the most common type of leukemia in young children. It also affects adults.

4. Acute myeloid leukemia. It occurs in both adults and children.

Risk factors

People exposed to very high levels of radiation are much more likely than others to develop leukemia. Very high levels of radiation have been caused by atomic bomb explosions (such as those in Japan during World War II) and nuclear power plant accidents (such as the Chernobyl accident in 1986).

Medical treatment that uses radiation can be another source of high-level exposure. Radiation used for diagnosis, however, exposes people to much lower levels of radiation and is not linked to leukemia.

Exposure to high levels of benzene in the workplace can cause leukemia. Benzene is used widely in the chemical industry. Formaldehyde is also used by the chemical industry. Workers exposed to formaldehyde also may be at greater risk of leukemia.

Cancer patients treated with certain cancer-fighting drugs sometimes later develop leukemia.

Down syndrome and certain other genetic diseases caused by abnormal chromosomes may increase the risk of leukemia.

One virus causes a rare type of chronic lymphocytic leukemia known as human T-cell leukemia. However, leukemia does not appear to be contagious.

In the past, some studies suggested exposure to electromagnetic fields as another possible risk factor for leukemia. Electromagnetic fields are a type of low-energy radiation that comes from power lines and electric appliances.

Symptoms

Like all blood cells, leukemia cells travel through the body. Depending on the number of abnormal cells and where these cells collect, patients with leukemia may have a number of symptoms.

Common symptoms of leukemia may include:

-              Fevers or night sweats

-              Frequent infections

-              Feeling weak or tired

-              Headache

-              Ability of bleeding and bruising easily (bleeding gums, purplish patches in the skin, or tiny red spots under the skin)

-              Pain in the bones or joints

-              discomfort in the abdomen (from an enlarged spleen)

-              Swollen lymph nodes, especially in the neck or armpit

-              Weight loss

In the early stages of chronic leukemia, the leukemia cells function almost normally. Symptoms may not appear for a long time. Doctors often find chronic leukemia during a routine checkup—before there are any symptoms. When symptoms do appear, they generally are mild at first and get worse gradually.

In acute leukemia, symptoms appear and get worse quickly. People with this disease go to doctor because they feel sick. Other symptoms of acute leukemia are vomiting, loss of muscle control. Leukemia cells also can collect in the testicles and cause swelling. Also, some patients develop sores in the eyes or on the skin. Leukemia also can affect the digestive tract, kidneys, lungs.