Acute lymphoblastic leukemia (ALL) is a type of cancer that causes the body to make too many white blood cells (lymphocytes). But these lymphocytes, called leukemia cells, cannot fight infection very well.

When leukemia cells build up in the blood and bone marrow, there is less room for healthy blood cells. This can cause infections, anemia, and easy bleeding.

ALL usually gets worse quickly. It is sometimes referred to as acute lymphocytic leukemia.