Acute lymphocytic leukemia (ALL) results from an acquired (not inherited) genetic injury to the DNA of a single cell in the bone marrow. The disease is often referred to as acute lymphoblastic leukemia because the leukemic cell that replaces the normal marrow is the (leukemic) lymphoblast. The effects are: 1) the uncontrolled and exaggerated growth and accumulation of cells called "lymphoblasts" or "leukemic blasts " which fail to function as normal blood cells and 2) the blockade of the production of normal marrow cells, leading to a deficiency of red cells (anemia), platelets (thrombocytopenia), and normal white cells (especially neutrophils, i.e., neutropenia) in the blood.
You might see the following symtoms:
You diagnose this with a blood test. The cells need to be examined under a microscope to see if they are the correct type.