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Leukemia is a type of cancer that affects white blood cells. Because there are many forms of leukemia, prompt attention and an effective diagnosis are important in determining the most successful route of treatment.
In 2009, an estimated 44,790 new cases of leukemia were diagnosed in the United States. Leukemia affects the tissue in the cells that form blood, specifically, white blood cells, which help to fight infection. In a person with leukemia, the bone marrow contains abnormal white blood cells. When too many abnormal white blood cells are present, they may destroy normal blood cells, leaving the person susceptible to infection. There are several types of leukemia. Each type affects a different kind of white blood cell.
Leukemia can be classified based on how quickly the disease develops. Leukemia can be either chronic, meaning the disease progresses slowly, and is difficult to diagnose early, or acute, meaning the number of leukemia cells increases rapidly.
The majority of leukemia cases can be diagnosed as one of the following types:
These types are named for the type of white blood cell affected.
Other rare types of leukemia include:
These cases account for fewer than 6,000 cases each year.
The exact causes of leukemia are unknown. Some factors that may increase risk are: