There are many different types of leukemia. Some are fast-growing and aggressive, others are slower to progress. Leukemias are also classified based on the type of blood cells affected. The most common types of leukemia include:
Acute leukemia involves an overgrowth of very immature blood cells, also known as blasts. This condition is life-threatening because there are not enough mature blood cells to prevent anemia, infection and bleeding. A diagnosis of acute leukemia is made when there are 20 percent or more blasts in the bone marrow. Acute lymphoblastic leukemia (ALL) is most common during childhood and in early adulthood, although it is also diagnosed in adults 30 years old and older. Acute myelogenous leukemia (AML) occurs more often in adults.
Chronic leukemia involves an overgrowth of mature blood cells. Usually, people with chronic leukemia have enough mature blood cells to prevent serious bleeding and infection. Chronic leukemia is more common in people between ages 40 and 70 and is rare among younger people.
Myelodysplastic Syndrome (MDS) is a condition in which the bone marrow does not function normally and does not produce enough normal blood cells. The blood cells affected are white blood cells, red blood cells and platelets. Some cases of MDS may progress to acute leukemia, over time. MDS is most often found in patients nearing their 60s and 70s.