Reviewed by Dr. Clement J. Cheng
Leukemia is a broad term used to describe cancer of the blood cells. Leukemia is marked by the body’s increased production of malignant white blood cells, which hinders the body’s manufacture of red blood cells, platelets, and healthy white blood cells.
Leukemia differs from other cancers because it does not produce tumors. Instead, it is defined as the widespread overproduction of cancerous white blood cells. In fact, the word “leukemia” is from the Greek words for “white” and “blood.”
Healthy blood contains white cells to fight disease, platelets to stanch wounds, and red cells to deliver oxygen to various parts of the body. Hundreds of billions of new blood cells are produced every day in the body’s bone marrow. Most of these cells are red blood cells, but people with leukemia start producing more white blood cells than necessary. These abnormal white blood cells live longer than normal white blood cells and do not mature normally.
Leukemic white blood cells cannot fight infection like healthy white blood cells. As they multiply, they interfere with the production of healthy blood cells, which leads to a deficit of red blood cells, platelets, and normal white blood cells. Leukemia patients become anemic and susceptible to bruising, bleeding, and infection.
More than 25,000 people are diagnosed with leukemia annually, most over the age of 65. More men are diagnosed than women, and more Caucasians than African-Americans. It is found 10 times more often in adults than in children, although one type of leukemia is considered a child’s disease.
Four major types of leukemia exist: acute lymphocytic, acute granulocytic, chronic granulocytic, and chronic lymphocytic. In acute leukemia, disease progression is rapid—the cancerous cells quickly crowd normal cells out of the bone marrow. Chronic leukemia progresses more slowly; functioning blood cells remain at nearly normal levels until later in the disease.
Acute lymphocytic leukemia (ALL) and acute granulocytic leukemia (AGL): ALL, also called childhood leukemia, develops when lymphocytes, a type of white blood cell that fights viruses and infections, reproduce rapidly in the bone marrow and blood. AGL occurs when a granulocyte, another type of white blood cell, becomes cancerous and reproduces unchecked. AGL is also called acute myelogenous leukemia (AML).
Bone marrow produces granulocytes; lymph glands and bone marrow produce lymphocytes. Granulocytes and lymphocytes normally start out as immature cells called blasts and develop into healthy, mature white blood cells. However, for people with ALL and AGL, these blasts fail to mature and start to overpopulate the bone marrow, blood, and lymph glands. As a result, the bone marrow cannot produce enough red blood cells, platelets, or healthy white blood cells.
ALL is more common in children; AGL is more common in adults. Although experts believe that it is not inherited, the exact cause is unknown.
Chronic granulocytic leukemia (CGL): CGL (also called CML) is the uncontrolled production of granulocytes in the bone marrow. The leukemic cells are generally more mature than in ALL or AGL, which results in the granulocyte levels rising dramatically.
CGL usually affects people over age 50. People exposed to radiation are at a slightly higher risk to develop the disease. Many people with CGL have an acquired chromosomal abnormality, the Philadelphia chromosome. This abnormality is present when portions of two different chromosomes are switched, causing rampant proliferation of white blood cells.
CGL is split into two disease phases. The first phase is relatively mild and lasts for three to five years. It is followed by a “blast transformation.” A blast transformation happens when the blood fills with blast cells, or immature white blood cells. During the second phase, the symptoms of CGL will mirror those of AGL.
Chronic lymphocytic leukemia (CLL): An excessive number of lymphocytes exist in the blood, lymph glands, spleen, and bone marrow in CLL. As the disease progresses, the malignant lymphocytes spread to other tissues. This results in the swelling of the lymph glands, the liver, and the spleen. The body becomes unable to fight infection effectively.
CLL is the most common leukemia in the United States. It mainly affects people over age 50. Most people with this type of cancer exhibit no symptoms and are diagnosed with the results of a blood test performed for another disease. Sometimes people with CLL require no treatment, and the disease will not get worse for 10 to 15 years. However, the average person with CLL will live 6 years after diagnosis. Twenty-five percent of CLL patients live for over 10 years after diagnosis and die of other causes. The earlier the diagnosis, the better the prognosis generally is.