Bone marrow stem cells are not involved. The disease remains stable for years and then transforms into acute myelogenous leukemia. Ph chromosome is recognized by cytogenetic studies to be a reciprocal translocation between the long arm of chromosome 9 and 22, leading to the formation of a hybrid gene. Expression of that gene leads to the induction of leukemic transformation of the affected cell. The etiology of the disease is not clear.
Radiation is believed to be one of the known causes.
Patients are usually over age of 60. The initial phase is the chronic phase, which can be either symptomatic or asymptomatic. Patients presenting in the blastic phase are more likely to have symptoms of anemia, infection and bleeding in addition to weight loss, fever, night sweats and bone pain. On examination, huge splenomegaly is the most common finding. The WBC count shows a full spectrum of mature and immature myeloid cells with peaks of myelocytes and mature neutrophils.