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Acute lymphoblastic leukemia (ALL), also called acute lymphocytic leukemia or acute lymphoid leukemia, is a fast-growing cancer of a type of white blood cells called lymphocytes. Normal lymphocytes help your body fight infections. In ALL, the lymphocytes are cancerous and don't fight infections very well. These cancerous cells (or leukemic blasts) grow quickly and crowd out the bone marrow, preventing it from making the normal red blood cells, white blood cells, and platelets that your body needs.

About 6,000 people in the United States are diagnosed with ALL each year.1 It is the most common type of leukemia in children under age 15.1 However, it can affect people of any age. The cause of ALL is unknown.

Learn more:

1. Howlader N, Noone AM, Krapcho M, Garshell J, Neyman N, Altekruse SF, Kosary CL, Yu M, Ruhl J, Tatalovich Z, Cho H, Mariotto A, Lewis DR, Chen HS, Feuer EJ, Cronin KA (eds). SEER Cancer Statistics Review, 1975-2010, National Cancer Institute. Bethesda, MD, http://seer.cancer.gov/csr/1975_2010/, based on November 2012 SEER data submission, posted to the SEER website, April 2013.