Chronic Lymphocytic Leukemia (CLL)

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What Is Leukemia?

Leukemia is a cancer that disrupts the normal development of blood cells. Inside most of your bones is a soft spongy material called bone marrow in which blood stem cells (immature blood cells) are produced. A blood stem cell becomes one of two types of stem cells: myeloid or lymphoid, each of which matures into different kinds of blood cells.

Myeloid stems cells become one of the following:

  • Red blood cells that carry oxygen to and from the tissues in your body
  • Platelets that help your blood to clot to control bleeding
  • Infection-fighting white blood cells known as granulocytes

Lymphoid stem cells become lymphoblasts, which mature into one of the following types of white blood cells:

  • B lymphocytes (B cells), which produce antibodies that identify and destroy bacteria and viruses
  • T lymphocytes (T cells), which fight against viruses and stimulate B cells to produce antibodies
  • Natural killer (NK) cells, which kill tumor cells and disease-carrying microorganisms

With chronic lymphocytic leukemia (CLL), lymphocytes stop maturing and don’t die off like normal lymphocytes. As a result, these abnormal white blood cells slowly start to crowd out the healthy red and white blood cells and platelets, preventing them from effectively bringing oxygen to needed tissues, fighting infection and stopping bleeding. This in turn can cause anemia, infection and easy bleeding.

Over the past 10 years, doctors have come to believe that there may be two forms of CLL—one that progresses very slowly and another that behaves more aggressively. Tests can determine which form you may have.