Chronic lymphocytic leukaemia developing in the course of chronic myeloid leukaemia.

Both chronic myeloid leukaemia (CML) and chronic lymphocytic leukaemia (CLL) are rare illnesses. Their co-existence has been previously reported, typically with CML following CLL. We report to our knowledge the first case of CLL developing some years after initial diagnosis of Philadelphia (Ph) chromosome positive CML. We provide molecular evidence that CLL arose in a Ph negative clone. The implications of the findings are discussed.