Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Acute lymphocytic leukemia (ALL) is a type of leukemia. Leukemia is a cancer of the blood or bone marrow. ALL is also known as acute lymphoblastic leukemia and acute lymphoid leukemia.

ALL is acancer of the body's blood-making system. Blood cells are produced in the bone marrow, the soft, inner part of bones.

The word "acute" in acute lymphocytic leukemia refers to the fact that the disease can progress quickly. The word "lymphocytic" means that the cancer develops from lymphocytes, a type of white blood cell.

The body produces three types of infection-fighting lymphocytes:

  • B lymphocytes, which make antibodies to help protect the body from germs.

  • T lymphocytes, which can destroy virus-infected cells, foreign cells, and cancer cells.

  • Natural killer cells, which also can kill cancer cells and viruses.

In ALL, the body produces too many immature lymphocytes (lymphoblasts). These cells cannot fight infection as well as normal cells.

In addition, as these lymphocytes quickly multiply, they crowd out healthy white blood cells, red blood cells, and platelets in the blood and bone marrow. This may lead to infection, anemia, and easy bleeding.

Certain genetic changes are also associated with ALL.

Acute lymphocytic leukemia typically invades the blood quickly. It can involve other parts of the body, such as the lymph nodes, liver, spleen, brain and spinal cord (central nervous system), and testes.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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