Acute lymphoblastic leukemia (ALL) is a cancer of the white blood cells in the bone marrow. The white blood cells (lymphocytes) grow in the bone marrow, then travel throughout the body to fight infections.

ALL also causes the bone marrow to make too many of these cells. The overgrowth makes it difficult for other blood cells like red blood cells or platelets to develop. Low levels of other blood cells can cause a variety of symptoms such as bleeding problems, fatigue and shortness of breath.

White Blood Cells
White Blood Cells
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The cause of ALL is unknown. Many cancers are believed to be caused by a combination of genetic and environmental factors.