Illustration of a transformed myeloid stem cell associated with the disease chronic myeloid leukaemia (CML). CML is a cancer of the myeloid cells caused by a genetic change in the stem cells, allowing the release of many partially mature cells. These cells accumulate in the bone marrow and prevent the production of other healthy blood cells such as red blood cells, platelets, and white blood cells. Although affected cells are partially mature, they generally cannot perform immune functions as well as mature cells.