Acute lymphocytic leukemia is uncommon among adults — about 2,410 will develop the disease in the United States this year — but ALL is the most common childhood cancer. Among adults, the incidence of ALL increases with age. ALL is less common among African Americans than among whites although scientists are unsure why. (For information about our services for children with leukemia, please visit Pediatric Leukemias.)
How ALL Develops
Like other blood cells, lymphocytes evolve from immature cells called hematopoietic stem cells. Stem cells are produced in the bone marrow and usually mature, or differentiate, into one of a range of different kinds of blood cells. Lymphocytic stem cells mature into T lymphocytes (T cells), B lymphocytes (B cells), or natural killer (NK) cells. Each of these has a specialized role in the immune system. Normal, healthy lymphocytes evolve through their life cycle in an orderly way and eventually die, to be replaced by new cells.
In acute lymphocytic leukemia (ALL) the DNA of the diseased cells is damaged, and the cells cannot mature beyond an early stage in their life cycle to become functional. Instead, the immature cells (called leukemic blasts or lymphoblasts) reproduce rapidly, take over the bone marrow, and displace the normal red and white blood cells and platelets that are produced there. As the numbers of normal cells fall, patients may experience anemia (a lack of oxygen-carrying red blood cells); infections caused by low counts of disease-fighting white blood cells; and bruising and bleeding resulting from low levels of platelets (the blood component that plays a crucial role in blood clotting and wound healing). Leukemic cells may also invade the liver, spleen, lymph nodes, and other organs.
Certain inherited, or genetic, diseases increase a person’s chances for developing ALL. People who are exposed to high doses of radiation (from the explosion of an atomic bomb, working in an atomic weapons plant, or from a nuclear reactor accident) have a heightened risk of developing this form of leukemia.
Many people with one or more of these risk factors never develop leukemia. In fact, most people who develop ALL have no known risk factors. Scientists do know that most types of leukemia are associated with specific gene mutations — alterations in the DNA of the diseased cells — but in the majority of cases it is not clear what causes those mutations.
The symptoms of acute leukemia generally appear suddenly and can be similar to those of a virus or flu. Symptoms can be severe enough that they prompt patients to see a doctor soon after their onset.
Symptoms can include:
- loss of weight and/or appetite
- tiny red spots in the skin
- easy bruising and/or bleeding
- weakness and fatigue
- coughing, shortness of breath
- frequent minor infections or poor healing of minor cuts
- swollen lymph nodes
- bone or joint pain
- difficulty maintaining balance
- blurred vision
- seizures, vomiting
- (for men) an enlarged, painless testicle
These symptoms are associated with a wide range of conditions and illnesses, but if these problems persist, consult a physician.