Chronic Myeloid leukemia o Chronic myeloid leukemia is a stem cell disease that is characterized by leucocytosis with granulocyc immaturies, basophilia, splenomegaly and disnct chromosomal abnormality - Philadelphia (Ph') chromosome. It is one of the chronic myeloproliferave disorders. Pathogenesis of chronic mveloid leukemia o CML is an acquired disease of haemopoiec stem cell and Ph’ chromosome is demonstrable in erythroid, myeloid and megakaryocyc precursors. Philadelphia chromosome BCR-ABL fusion gene Philadelphia chromosome is formed as a result of reciprocal translocaon between long arm of chromosome 22 and chromosome 9 i.e. + (9:22) ABL proto-oncogene from chromosome 9 is translocated to chromosome 22 where BCR is present and results in formaon of BCR-ABL fusion chimeric gene BCR ABL gene is hallmark of CML.