Chronic lymphocytic leukemia (CLL) is a type of cancer of the blood and bone marrow — the spongy tissue inside bones where blood cells are made.

The term "chronic" in chronic lymphocytic leukemia comes from the fact that this leukemia typically progresses more slowly than other types of leukemia. The term "lymphocytic" in chronic lymphocytic leukemia comes from the cells affected by the disease — a group of white blood cells called lymphocytes, which help your body fight infection.

Chronic lymphocytic leukemia most commonly affects older adults. There are treatments to help control the disease.


Many people with chronic lymphocytic leukemia have no symptoms at first. Signs and symptoms might develop as the cancer progresses. They might include:

  • Enlarged, but painless, lymph nodes
  • Fatigue
  • Fever
  • Pain in the upper left portion of the abdomen, which may be caused by an enlarged spleen
  • Night sweats
  • Weight loss
  • Frequent infections

When to see a doctor

Make an appointment with your doctor if you have any persistent signs and symptoms that worry you.


Doctors aren't certain what starts the process that causes chronic lymphocytic leukemia. What's known is that something happens to cause changes (mutations) in the DNA of blood-producing cells. A cell's DNA contains the instructions that tell the cell what to do. The changes tell the blood cells to produce abnormal, ineffective lymphocytes.

Beyond being ineffective, these abnormal lymphocytes continue to live and multiply when healthy lymphocytes would die. The abnormal lymphocytes accumulate in the blood and certain organs, where they cause complications. They may crowd healthy cells out of the bone marrow and interfere with blood cell production.

Doctors and researchers are working to understand the exact mechanism that causes chronic lymphocytic leukemia.

Risk factors

Factors that may increase the risk of chronic lymphocytic leukemia include:

  • Your age. This disease occurs most often in older adults.
  • Your race. White people are more likely to develop chronic lymphocytic leukemia than are people of other races.
  • Family history of blood and bone marrow cancers. A family history of chronic lymphocytic leukemia or other blood and bone marrow cancers may increase your risk.
  • Exposure to chemicals. Certain herbicides and insecticides, including Agent Orange used during the Vietnam War, have been linked to an increased risk of chronic lymphocytic leukemia.
  • A condition that causes excess lymphocytes. Monoclonal B-cell lymphocytosis (MBL) causes an increased number of one type of lymphocyte (B cells) in the blood. For a small number of people with MBL, the condition may develop into chronic lymphocytic leukemia. If you have MBL and also have a family history of chronic lymphocytic leukemia, you may have a higher risk of developing cancer.


Chronic lymphocytic leukemia may cause complications such as:

  • Frequent infections. If you have chronic lymphocytic leukemia, you may experience frequent infections that can be serious. Sometimes infections happen because your blood doesn't have enough germ-fighting antibodies (immunoglobulins). Your doctor might recommend regular immunoglobulin infusions.
  • A switch to a more aggressive form of cancer. A small number of people with chronic lymphocytic leukemia may develop a more aggressive form of cancer called diffuse large B-cell lymphoma. Doctors sometimes refer to this as Richter's syndrome.
  • Increased risk of other cancers. People with chronic lymphocytic leukemia have an increased risk of other types of cancer, including skin cancer and cancers of the lung and the digestive tract.
  • Immune system problems. A small number of people with chronic lymphocytic leukemia may develop an immune system problem that causes the disease-fighting cells of the immune system to mistakenly attack the red blood cells (autoimmune hemolytic anemia) or the platelets (autoimmune thrombocytopenia).

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