Leukemia is a cancer of the blood and bone marrow. The bone marrow is the spongy center of the bones that make blood cells. Although leukemia starts in the blood it eventually affects all parts of the body. Currently, the ultimate cause and cure for leukemia remains unknown. Although we do not know its cause or cure, we do know that leukemia strikes people of all ages, races and genders. In children, it remains the leading cause of death by disease. Adults over 60 remain the highest risk age group, responding least successfully to current treatments. Persons with Down’s syndrome and certain other genetic abnormalities have higher than normal incidences of leukemia. Leukemia has also been linked to excessive exposure to ionizing radiation and to certain chemicals such as benzene, a toxic, commercially used substance. Certain forms of leukemia and lymphoma are caused by a retrovirus, HTLV-1.
To understand how leukemia affects the blood, it is important to know the components of normal blood and how it functions. Normal blood is made up of plasma and three main types of blood cells; white cells, red cells, and platelets. White blood cells help the body fight infection. Red blood cells contain hemoglobin that picks up oxygen from the lungs and carries it to the body’s organs. Platelets help form blood clots to control bleeding. Blood cells are produced inside the bones in a spongy space called the bone marrow. All blood cells have a common origin called a stem cell. Stem cells develop into specific mature blood cells by a process called differentiation. Once the cells mature they are released into the blood where they circulate throughout the body and perform their respective functions. In healthy individuals, there are adequate stem cells to continuously produce new blood cells. When leukemia occurs, abnormal white blood cells divide uncontrollably, crowding out the healthy cells of the bloodstream. These leukemic cells are immature, unable to perform their infection-fighting function. As they multiply, normal white blood cells, as well as the red blood cells and platelets are overwhelmed.
Most leukemias are classified as either myelocytic or lymphocytic, depending on the type of white blood cell that is affected. Leukemias are further divided into chronic or acute, depending on how fast the disease spreads. Acute leukemias progress rapidly, resulting in the accumulation of immature, functionless cells in the blood and bone marrow. Chronic leukemias progress more slowly, allowing a greater number of mature, functional cells to be produced.
While there are a number of types of leukemia, the four most commonly occurring types of leukemia are:
Acute Lymphoblastic Leukemia (ALL) ALL is a hematologic malignancy of uncontrolled progenitors. ALL is the most common childhood leukemia, but it accounts for only 20 percent of adult leukemias.
Acute Myelogenous Leukemia (AML) AML is a group of diseases in which an abnormal hematologic stem cell give rise to a monoclonal population of myeloid cells whose ability to differentiate beyond early forms is impaired. These abnormal cells have a growth advantage and eventually replace the normal cells. AML is the most common leukemia in adults.
Chronic Lymphocytic Leukemia (CLL) CLL is a hematologic malignancy characterized by proliferation and accumulation of relatively mature-looking, but immunological ineffective lymphocytes. CLL is the most common leukemia in Western countries and generally occurs in older individuals (median age is 60), although occasionally it can develop in young adults and even children. CLL occurs twice as often in males as in females.
Chronic Myelogenous Leukemia (CML) CML is a hematologic malignancy that results from the development of an abnormal hematopoietic stem cell. CML is a clonal disorder in which the marrow cells with increased proliferation seem to have a growth advantage and to overproduce in the marrow itself, replacing normal myeloid cells and expanding into the peripheral blood. CML accounts for approximately twenty to thirty percent of all adult leukemias. CML is a relatively rare disease in children and occurs more frequently in men than women.
The early warning signs of leukemia may include fatigue, paleness, weight loss, repeated infections, bruising easily and nosebleeds or other hemorrhages. Children with leukemia can have few symptoms that occur slowly over a long period of time. Because symptoms often appear to be those of other, less serious conditions, leukemia can be difficult to diagnose early. When a physician suspects leukemia, it can be diagnosed in different ways. The most common place and way to detect leukemia is in the blood and bone marrow through a procedure called a Bone Marrow Aspirate and Biopsy. This procedure, typically performed on a hip bone, involves inserting a needle through the skin and into the middle of the bone. The needle then draws out a small amount of marrow which is then examined under a microscope and tested to distinguish which type of blood cell is cancerous and the aggressiveness of the cancer. There are several different treatment practices for leukemia patients. Chemotherapy and radiation are the most common and effective method of treating leukemia. Chemotherapy, kills the attacking abnormal cells with drugs while radiation uses x-rays to break down the bad cells. Transfusions of blood components and antibiotics are used as supportive treatments. Continuing research at leading medical centers is yielding new and better drugs for treating leukemia patients. Various anticancer drugs are used, either in combination or as a single agent. Under appropriate conditions, Bone Marrow Transplantation may be useful in the treatment of certain leukemia.
These websites provide additional information on leukemia:
National Cancer Institute
Federal Drug Administration