Leukemia is cancer that starts in the tissues that form blood.
The types of leukemia can be grouped based on how quickly the disease develops and advances. Leukemia is either chronic (which usually gets worse slowly) or acute (which usually gets worse quickly):
- Chronic leukemia: Early in the disease, the leukemia cells can still do some of the work of normal white blood cells. People may not have any symptoms at first. Doctors often find chronic leukemia during a routine checkup, before there are any symptoms. Slowly, chronic leukemia gets worse. As the number of leukemia cells in the blood increases, people get symptoms, such as swollen lymph nodes or infections. When symptoms do appear, they are usually mild at first and get worse gradually.
- Acute leukemia: The leukemia cells can’t do any of the work of normal white blood cells. The number of leukemia cells increases rapidly. Acute leukemia usually worsens quickly.