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

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 or myelogenous leukemia.

There are four common types of leukemia:

• Chronic lymphocytic leukemia (chronic lymphoblastic leukemia, or CLL) accounts for about 7,000 new cases of leukemia each year. Most often, people diagnosed with the disease are over age 55. It almost never affects children.
• Chronic myeloid leukemia (chronic myelogenous leukemia, or CML) accounts for about 4,400 new cases of leukemia each year. It affects mainly adults.
• Acute lymphocytic leukemia (acute lymphoblastic leukemia, or ALL) accounts for about 3,800 new cases of leukemia each year. It is the most common type of leukemia in young children. It also affects adults.
• Acute myeloid leukemia (acute myelogenous leukemia, or AML) accounts for about 10,600 new cases of leukemia each year. It occurs in both adults and children.

Hairy cell leukemia is a rare type of chronic leukemia.

Estimated new cases and deaths from leukemia in the United States each year:

•  New cases: 44,240
• Deaths: 21,790

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
• Bleeding and bruising easily (bleeding gums, purplish patches in the skin, or tiny red spots under the skin)
• Pain in the bones or joints
• Swelling or 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. Other symptoms of acute leukemia are 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.

Treatment

Depending on the type and extent of the disease, patients may have chemotherapy, biological therapy, radiation therapy, or bone marrow transplantation. If the patient’s spleen is enlarged, the doctor may suggest surgery to remove it. Some patients receive a combination of treatments.

People with acute leukemia need to be treated right away. The goal of treatment is to bring about a remission. Then, when signs and symptoms disappear, more therapy may be given to prevent a relapse. Many people with acute leukemia can be cured.

Chronic leukemia patients who do not have symptoms may not require immediate treatment. The doctor may suggest watchful waiting for some patients with chronic lymphocytic leukemia. Treatment will begin if symptoms occur or worsen. When treatment for chronic leukemia is needed, it can often control the disease and its symptoms. However, chronic leukemia can seldom be cured. Patients may receive maintenance therapy to help keep the cancer in remission.