Acute lymphoblastic leukemia, also known as
acute lymphocytic leukemia or
acute lymphoid leukemia (
ALL), is an
acute form of
leukemia, or
cancer of the white blood cells, characterized by the overproduction and accumulation of
cancerous, immature
white blood cells, known as
lymphoblasts. In persons with ALL, lymphoblasts are overproduced in the
bone marrow and continuously multiply, causing damage and death by inhibiting the production of normal cells (such as
red and
white blood cells and
platelets) in the bone marrow and by spreading (
infiltrating) to other organs. ALL is most common in childhood, with a peak incidence at 2–5 years of age and another peak in old age.