Types of Leukemia

There are several different types of leukemia. In general, leukemia is grouped by how fast it gets worse and what kind of white blood cell it affects.

It may be acute leukemia and chronic leukemia:

Acute leukemia is characterized by the rapid increase of immature blood cells. This crowding makes the bone marrow unable to produce healthy blood cells. Immediate treatment is required in acute leukemias due to the rapid progression and accumulation of the malignant cells, which then spill over into the bloodstream and spread to other organs of the body. Acute forms of leukemia are the most common forms of leukemia in children.

Chronic leukemia is distinguished by the excessive build up of relatively mature, but still abnormal, blood cells. Typically taking months or years to progress, the cells are produced at a much higher rate than normal cells, resulting in many abnormal white blood cells in the blood. Whereas acute leukemia must be treated immediately, chronic forms are sometimes monitored for some time before treatment to ensure maximum effectiveness of therapy. Chronic leukemia mostly occurs in older people, but can theoretically occur in any age group.

It may be lymphoblastic (lymphocytic) leukemias, and myeloid (myelogenous) leukemias:

Lymphoblastic leukemias involve progressive bone marrow failure but with an insufficient proportion of blast cells (< 30%) for making a definite diagnosis of AML; 40 to 60% of cases evolve into AML.

Myeloid leukemias's reaction is marked granulocytic leukocytosis (ie, WBC > 30,000/μL) produced by normal bone marrow in response to systemic infection or cancer. Although not a neoplastic disorder, a leukemoid reaction with a very high WBC count may require testing to distinguish it from CML (see Leukemias: Chronic Myelocytic Leukemia (CML)).

Congregation these two classifications provides four main types:
Acute lymphoblastic leukemia (ALL) is the most common leukemia in children. Adults can also get it.
Acute myelogenous leukemia (AML) affects both children and adults.
Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults, mostly those who are older than 55. Children almost never get it. It sometimes runs in families.
Chronic myelogenous leukemia (CML) occurs mostly in adults.
Another less common type is called hairy cell leukemia, a chronic condition in which the lymphocytic cells develop projections, about 80% of affected people are adult men.