Acute lymphoblastic leukemia , also known as acute lymphocytic leukemia, characterized by the overproduction and accumulation of cancerous, immature white blood cells, known as lymphoblasts, 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. Acute lymphoblastic leukemia is most common in childhood, with a peak incidence at 2-5 years of age and another peak in old age.