Leukemia is classified by how quickly it progresses. Acute leukemia is fast-growing and can overrun the body within a few weeks or months. By contrast, chronic leukemia is slow-growing and progressively worsens over years.
Acute versus Chronic Leukemia
The blood-forming (hematopoietic) cells of acute leukemia remain in an immature state, so they reproduce and accumulate very rapidly. Therefore, acute leukemia needs to be treated immediately, otherwise the disease may be fatal within a few months. Fortunately, some subtypes of acute leukemia respond very well to available therapies and they are curable. Children often develop acute forms of leukemia, which are managed differently from leukemia in adults.
In chronic leukemia, the blood-forming cells eventually mature, or differentiate, but they are not "normal." They remain in the bloodstream much longer than normal white blood cells, and they are unable to combat infection well.