Leukemia is the general name for different cancers of the blood or bone marrow. In leukemia, "abnormal," or cancerous white blood cells grow and multiply in the bone marrow. Most patients with leukemia have very high numbers of white blood cells. These extra cells don’t work in a normal way. Over time, they crowd out normal blood cells and can keep them from working, too.
The ways that people are affected by their cancer and the rate at which the cancer progresses are different for each type of leukemia. Some leukemias develop quickly ("acute leukemia") and others develop over a much longer period of time ("chronic leukemia"). Both acute and chronic myeloid leukemias develop from immature myeloid cells, a kind of white blood cell. Acute and chronic lymphocytic leukemias develop from immature lymphocytes, another kind of white blood cell.
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In chronic lymphocytic leukemia (CLL), the abnormal white blood cells (CLL cells) do not prevent normal blood cell production as much as with some other forms of leukemia. This is the reason that early stages of CLL are much less severe than other forms of leukemia. Some patients with early-stage CLL have a high white blood cell count but no symptoms except, perhaps, a recurring infection. During this period, healthcare professionals may "watch and wait" instead of prescribing treatment. "Watch and wait" means that healthcare professionals will watch for signs and symptoms of disease and wait until the disease progresses before starting treatment. The watch-and-wait stage can last for many years in some patients. Other patients may require treatment at the time of diagnosis or soon after diagnosis.
More people have CLL than any other form of leukemia. About 15,000 new cases of CLL are diagnosed in the United States every year. Most people with CLL are over 50 years old.
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