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What is chronic lymphocytic leukemia (CLL)?

CLL – a leukemia of the blood or bone marrow.

One of 4 main types of leukemia, CLL is a cancer of the blood and bone marrow. Bone marrow is the soft tissue inside bones where blood cells are made. CLL affects a group of cells called lymphocytes. Lymphocytes are the white blood cells that are part of the lymphatic system and help your body fight infection.

CLL usually starts with a mutation, or abnormal change, to the DNA of a single lymphocyte. Over time, the CLL cells multiply faster than normal cells. Eventually, the CLL cells crowd out the healthy, disease-fighting cells.

With medical care, many people live with CLL for years without experiencing any symptoms at all. It’s estimated that approximately 86,000 people in the United States are living with, or are in remission from, CLL.

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US.XON.10.04.015 Last Update: May 2010