What's the etiology of chronic leukemia?

Usually sporadic: CML is associated with a known genetic abnormality (t(9;22) - otherwise known as the philadelphia chromosome). It is not known what in the environment 'causes' this. Chronic lymphocytic leukemia has different common genetic changes, the causes of which also are not known. Rarely though, cll seems to run in families. This has led to significant research into what genetic drivers may be found.

Wish I knew.: There is some evidence that excessive exposure to chemicals such as benzene may lead to an increased incidence of chronic myeloid leukemia, and excessive exposure to radiation has also been implicated. Cllhas been linked to pesticide exposure in some-but not all-studies. In animals, diseases like cll are usually caused by a virus. In practice a doctor rarely finds the cause of a patients leukemia.