Leukemia is a type of cancer that affects the blood and bone marrow. It occurs when the body produces an excessive number of abnormal white blood cells, which can interfere with the production of normal blood cells. This can lead to symptoms such as fatigue, frequent infections, and easy bruising or bleeding. There are several types of leukemia, including acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML). Diagnosis typically involves blood tests and bone marrow examinations. Treatment options may include chemotherapy, radiation therapy, and stem cell transplants, depending on the type and severity of the disease.