What is chronic myeloid leukemia?

Chronic myeloid leukemia (CML or chronic myelogenous leukemia) is a disease in which too many white blood cells are made in the bone marrow. Normally, bone marrow cells called blasts develop into several different types of blood cells. Chronic myeloid leukemia (CML) affects the blasts that are developing into white blood cells. In most people with CML, the genetic material (chromosomes) in the leukemia cells have an abnormal feature called a Philadelphia chromosome. Leukemia can be acute (progressing quickly) or chronic (progressing slowly). Chronic myeloid leukemia progresses slowly and usually occurs in people who are middle-aged or older, although it can also occur in children.