Leukemia is often initially defined by how quickly the disease develops and progresses—either as chronic which progresses slowly or acute which progresses rapidly.

In chronic leukemia, particularly in the early stages, the abnormal blood cells still function and people who have the disease may remain asymptomatic for varying lengths of time. Slowly, as the aberrant leukemia cells in the blood increase, symptoms appear.

In acute leukemia, the abnormal leukemia cells multiply rapidly, causing symptoms to progress quickly. Because of the lack of fully mature and functional cells in the blood—such as white and red blood cells—anemia and infection occur in persons with this type of cancer. Persons with acute leukemia may bleed extensively since the disease may attack the particle that helps blood clot.

Common symptoms of leukemia may include frequent infections, fevers or night sweats, weakness and/or fatigue, headache, bleeding and bruising easily, pain in the bones or joints, swelling or discomfort in the abdomen (resulting from an enlarged spleen), swollen lymph nodes, especially in the neck or armpit and unexplained weight loss.

The diagnosis of leukemia is made through a series of blood tests and a bone marrow examination. Additional tests are needed to confirm the diagnosis and to determine the type of leukemia and the extent to which it is present in one’s body.

The types of leukemia are grouped by the type of white blood cell affected. Leukemia that affects lymphoid cells is called lymphocytic leukemia. Leukemia that affects myeloid cells is called myeloid leukemia or myelogenous leukemia. Both types—lymphocytic and myeloid—can progress slowly (chronic) or rapidly (acute.)

Chronic lymphocytic leukemia accounts for about 7,000 new cases of leukemia each year, most often in people over age 55. It almost never affects children. Chronic myeloid leukemia accounts for about 4,400 new cases of leukemia each year, again, mainly affecting adults.

Acute lymphocytic leukemia accounts for about 3,800 new cases of leukemia each year. While it is the most common type of leukemia in young children, it can also affect adults. Acute myeloid leukemia is the most frequently occurring iteration of leukemia with approximately 10,600 new cases diagnosed each and can occur in both children and adults.

We do not know the exact cause of leukemia, but several potential risk factors have been identified:

• hereditary and genetic variables,
• some drugs used to treat other types of cancers,
• exposure to high doses of radiation,
• agricultural and industrial chemicals such as benzene and formaldehyde,
• certain viruses and diseases (for example, people with Down Syndrome face an increased risk of leukemia).

Chemotherapy is the major form of treatment for leukemia. The therapy given may include only a single chemical agent or a combination. Other therapies include:

• bone marrow transplant
• drug therapy—typically with Interferon, an antiviral agent that works to stop the spread of leukemic cells and helps bolster the immune system or Cladribine, a drug that destroys both dividing leukemic cells and cells that are at rest, or Imatinib mesylate/Gleevec recently approved by the FDA as a treatment for people newly diagnosed with chronic myeloid leukemia
• Stem cell transplant
• Cell-specific antibodies that destroy leukemic cells
• Radiation therapy
• Retinoic acid which prematurely ages and kills leukemic cells.

More specific information is available at the following links:

Mayo Clinic
Leukemia and Lymphoma Society
WebMD
Medline
National Cancer Institute