The disease before leukemia is typically acute lymphocytic leukemia (ALL). ALL is a type of cancer that starts in the white blood cells, which are the cells that fight infection. It is the most common type of leukemia among children, but it can also occur in adults. Symptoms of ALL include fatigue, fever, weight loss, frequent infections, and easy bruising and bleeding. Treatment for ALL typically includes chemotherapy, radiation therapy, and stem cell transplants.