Definition: Leucemia, also known as acute myeloid leukemia (AML), is a type of blood cancer. It occurs when abnormal cells in your body grow and divide too quickly, which can lead to serious symptoms like bleeding, fatigue, or loss of appetite. The exact cause is not fully understood, but it's believed that certain genes are more likely to be affected by AML. A common symptom of leucemia is bone pain, as the bone marrow (red blood cells) produces too