A two-panel drawing of normal blood cells and blood cells with leukaemia, showing platelets (blue), red blood cells (red), white blood cells (light purple), plasma (green arrow), and blast cells (orange). Leukaemia is a group of cancers that usually begin in the bone marrow and result in high numbers of abnormal white blood cells. The exact cause of leukaemia is unknown. Different kinds of leukaemia are believed to have different causes. Both inherited and environmental (non-inherited) factors are believed to be involved. Risk factors include smoking, ionizing radiation, some chemicals (such as benzene), prior chemotherapy, and Down syndrome. People with a family history of leukaemia are also at higher risk. |