Understanding Leukemia

Leukemia is a form of cancer that generally occurs when the body makes too many blood cells. It’s important to know:

  • Leukemia comes in many types and subtypes.
  • Doctors don’t know what causes it, but genetics and environmental factors may play a role.
  • Survival rates have improved in recent decades because of groundbreaking advances.
  • Advances include Gleevec, a targeted medication developed through research by Knight Cancer Institute Director Brian Druker, M.D.
  • Most leukemia patients are older than 55 when diagnosed, but leukemia is also the most common cancer in children.


A diagram showing the bloodstream of a healthy child, and the bloodstream of a child with leukemia.
In leukemia, a blood cancer, abnormal white blood cellscan outnumber and crowd out normal blood cells.

What is leukemia?

Leukemia is a cancer in which blood cells, usually white blood cells, grow abnormally and don’t work properly. Normally, white blood cells form in bone marrow and travel through the body to fight infection. With leukemia, malformed white cells outnumber the body’s other blood cells:

  • Red blood cells that carry oxygen throughout the body (oxygenation)
  • Platelets that help blood to clot

This imbalance erodes organ function. It also hurts the ability of red blood cells and platelets to do their jobs. The leukemia cells don’t fight infection as well. 

Who gets leukemia?

An estimated 60,650 people are expected to be diagnosed with leukemia in the U.S. in 2022. In 2019, about 473,000 people in the U.S. were living with leukemia, according to the National Cancer Institute.

Leukemia’s exact cause is unknown. The disease may have a hereditary component. Risk factors include:

  • Gender: Some types of leukemia are more common in men.
  • Age: About three in four patients are 55 or older at diagnosis.
  • Family history: Having a close relative such as a parent or sibling raises risk.
  • Genetic disorders: Down syndrome, neurofibromatosis (marked by tumors in the nervous system) and other genetic disorders come with higher risk.
  • Medical history: Previous chemotherapy or radiation therapy can increase risk.
  • Chemical exposure: Smoking raises your risk. Exposure to benzene increases risk of acute lymphoblastic leukemia, or AML. Exposure to the herbicide Agent Orange increases risk of chronic lymphocytic leukemia, or CLL.

Survival rates for leukemia

The overall survival rate for all types of leukemia has nearly doubled since 1975. Now, patients with leukemia are 65% as likely to live at least five years after diagnosis compared with the general population. This is called the relative survival rate. Survival rates are higher for certain types of leukemia and for patients younger than 15.

It’s important to remember that these rates are averages, and can’t predict the outcome for any individual. Also, by definition, five-year survival rates reflect the treatments that were available five or more years ago.

Leukemia symptoms

Symptoms vary by type. Some of the more common symptoms include:

  • Bruises for no apparent reason
  • Prolonged bleeding from minor cuts
  • Enlarged lymph nodes or pain on the left side under the ribs (from an enlarged spleen)
  • Fever without an obvious cause, nagging low-grade fever, chills or night sweats
  • Pale skin from having too few red blood cells (anemia)
  • Pinhead-size red spots under the skin (petechiae)
  • Frequent infections
  • Fatigue
  • Unexplained weight loss or loss of appetite
Leukemia symptoms graphic

Types of leukemia

Doctors classify leukemia by how fast it progresses and by the type of cell it affects:


  • Acute leukemia worsens quickly. It occurs when the abnormal cells are immature blood cells, called blasts, that multiply rapidly.
  • Chronic leukemia involves mature blood cells and progresses much more slowly.

Cell type

  • Lymphocytic leukemia affects cells that form lymphatic tissue, which is part of the immune system.
  • Myeloid leukemia affects myeloid cells, which form the three types of blood cells: red, white and platelets.

Types include:

  • Acute lymphoblastic leukemia (ALL), also called acutel lymphocytic leukemia, has no clear cause and can progress rapidly.
  • Acute myeloid leukemia (AML) progresses quickly without treatment and can be difficult to treat. It affects cells that aren’t fully developed.
  • Chronic lymphocytic leukemia (CLL) is the most common type in adults. Its progression varies.
  • Chronic myeloid leukemia (CML) is highly treatable when diagnosed early.
  • Hairy cell leukemia (HCL) is a rare type of chronic leukemia with a high survival rate.
  • Chronic myelomonocytic leukemia (CMML) is an uncommon blood cancer with an unclear cause.
  • Juvenile myelomonocytic leukemia (JMML) is a rare, rapidly progressing cancer that most often affects children six and younger. Learn more about our advanced care for pediatric leukemia at Doernbecher Children’s Hospital.
  • Large granular lymphocytic (LGL) leukemia affects white blood cells. There are two kinds, with different rates of progress.
  • Blastic plasmacytoid dendritic cell neoplasm (BPDCN) has features of leukemia and lymphoma. Lymphoma is another blood cancer related to an imbalance of infection-fighting cells. 

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