Chronic myelogenous leukemia (CML) is a type of cancer that causes the body to produce large numbers of white blood cells (myelocytes). These myelocytes, called leukemia cells, cannot fight infection very well.

When leukemia cells build up in the blood and bone marrow, there is less room for healthy blood cells. This can cause infections, anemia, and easy bleeding.

CML usually gets worse slowly. It is sometimes referred to as chronic myeloid leukemia or chronic granulocytic leukemia.

CML is more common in men than in women. It occurs more frequently in adults in their 50s and is rarely seen in children. Most people with CML have a gene change (mutation) called the Philadelphia chromosome.

Symptoms of CML include weakness and fatigue, fever, night sweats, poor appetite, and weight loss. The spleen may become swollen and painful.

CML is classified into three distinct phases: chronic phase, accelerated phase, and the blast crisis phase.