What Is Leukemia?

Leukemia is a type of cancer. Cancer is a group of more than 100 diseases that have two important things in common. One is that certain cells in the body become abnormal. Another is that the body keeps producing large numbers of these abnormal cells.

Leukemia is cancer of the blood cells. To understand leukemia, it is helpful to know about normal blood cells and what happens to them when leukemia develops.

Normal Blood Cells

The blood is made up of fluid called plasma and three types of cells. Each type has special functions.

• White blood cell (also called WBCs or leukocytes) help the body fight infections and other diseases.
• Red blood cells (also called RBCs or erythrocytes) carry oxygen from the lungs to the body's tissues and take carbon dioxide from the tissues back to the lungs. The red blood cells give blood its color.
• Platelets (also called thrombocytes) help form blood clots that control bleeding.

Blood cells are formed in the bone marrow, the soft, spongy center of bones. New (immature) blood cells are called blasts. Some blasts stay in the marrow to mature. Some travel to other parts of the body to mature.

Normally, blood cells are produced in an orderly, controlled way, as the body needs them. This process helps keep us healthy.

Leukemia Cells

When leukemia develops, the body produces large numbers of abnormal blood cells. In most types of leukemia, the abnormal cells are white blood cells. The leukemia cells usually look different from normal blood cells, and they do not function properly.

Types of Leukemia

There are several types of leukemia. They are grouped in two ways. One way is by how quickly the disease develops and gets worse. The other way is by the type of blood cell that is affected.

Leukemia is either acute or chronic. In acute leukemia, the abnormal blood cells are blasts that remain very immature and cannot carry out their normal functions. The number of blasts increases rapidly, and the disease gets worse quickly. In chronic leukemia, some blast cells are present, but in general, these cells are more mature and can carry out some of their normal functions. Also, the number of blasts increases less rapidly than in acute leukemia. As a result, chronic leukemia gets worse gradually.

Leukemia can arise in either of the two main types of white blood cells-- lymphoid cells or myeloid cells. When leukemia affects lymphoid cells, it is called lymphocytic leukemia. When myeloid cells are affected, the disease is called myeloid or myelogenous leukemia.

These are the most common types of leukemia:

• Acute lymphocytic leukemia (ALL) is the most common type of leukemia in young children. This disease also affects adults, especially those age 65 and older.
• Acute myeloid leukemia (AML) occurs in both adults and children. This type of leukemia is sometimes called acute nonlymphocytic leukemia (ANLL).
• Chronic lymphocytic leukemia (CLL) most often affects adults over the age of 55. It sometimes occurs in younger adults, but it almost never affects children.
• Chronic myeloid leukemia (CML) occurs mainly in adults. A very small number of children also develop this disease.

Symptoms

Leukemia cells are abnormal cells that cannot do what normal blood cells do. They cannot help the body fight infections. For this reason, people with leukemia often get infections and have fevers.

Also, people with leukemia often have less than the normal amount of healthy red blood cells and platelets. As a result, there are not enough red blood cells to carry oxygen through the body. With this condition, called anemia, patients may look pale and feel weak and tired. When there are not enough platelets, patients bleed and bruise easily.

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.

In acute leukemia, symptoms appear and get worse quickly. People with this disease go to their doctor because they feel sick. In chronic leukemia, symptoms may not appear for a long time; when symptoms do appear, they generally are mild at first and get worse gradually. Doctors often find chronic leukemia during a routine checkup--before there are any symptoms.

These are some of the common symptoms of leukemia:

• Fever, chills, and other flu-like symptoms;
• Weakness and fatigue;
• Frequent infections;
• Loss of appetite and/or weight;
• Swollen or tender lymph node, liver, or spleen;
• Easy bleeding or bruising;
• Tiny red spots (called petechiae) under the skin;
• Swollen or bleeding gums;
• Sweating, especially at night; and/or
• Bone or joint pain.
  

In acute leukemia, the abnormal cells may collect in the brain or spinal cord (also called the central nervous system or CNS). The result may be headaches, vomiting, confusion, loss of muscle control, and seizures. 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, or other parts of the body.

In chronic leukemia, the abnormal blood cells may gradually collect in various parts of the body. Chronic leukemia may affect the skin, central nervous system, digestive tract, kidneys, and testicles.

Diagnosis

To find the cause of a person's symptoms, the doctor asks about the patient's medical history and does a physical exam. In addition to checking general signs of health, the doctor feels for swelling in the liver; the spleen; and the lymph nodes under the arms, in the groin, and in the neck.

Blood tests also help in the diagnosis. A sample of blood is examined under a microscope to see what the cells look like and to determine the number of mature cells and blasts. Although blood tests may reveal that a patient has leukemia, they may not show what type of leukemia it is.

To check further for leukemia cells or to tell what type of leukemia a patient has, a hematologist, oncologist, or pathologist examines a sample of bone marrow under a microscope. The doctor withdraws the sample by inserting a needle into a large bone (usually the hip) and removing a small amount of liquid bone marrow. This procedure is called bone marrow aspiration. A bone marrow biopsy is performed with a larger needle and removes a small piece of bone and bone marrow.

If leukemia cells are found in the bone marrow sample, the patient's doctor orders other tests to find out the extent of the disease. A spinal tap (lumbar puncture) checks for leukemia cells in the fluid that fills the spaces in and around the brain and spinal cord (cerebrospinal fluid). Chest x-ray can reveal signs of disease in the chest.

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