 CML is a type of cancer in which the bone marrow produces too many red blood cells.This is caused by chromosomal translocation, a mutation in which the abnormal gene BCR-ABL, is turned into a CML cell.CML starts off as a myeloproliferative for example in sickle cell anemia or extreme granulocytosis but if left untreated, it could transform into an acute form of leukemia.