Master Chronic Myelogenous Leukemia (CML) with Picmonic for Medicine

Myeloproliferative disorders are characterized by increased production of one or more types of blood cells and are commonly associated with the presence of a mutated constitutively activated tyrosine kinase. Chronic myelogenous leukemia (CML) is a meyloprolfierative disorder characterized by the presence of a chimeric BCR-ABL gene derived from portions of the BCR gene on chromosome 22 and the ABL gene on chromosome 9 caused by (9;22) translocation. This is called a Philadelphia chromosome and this gene synthesizes a constitutively active BCR-ABL tyrosine kinase. Activation of this kinase induces pro-growth and pro-survival pathway that are normally turned on by hematopoietic growth factors. For unknown reasons, the BCR-ABL tyrosine kinase preferentially stimulates the proliferation of granulocytic and megakaryocytic progenitors and causes the abnormal release of immature granulocytic forms from the bone marrow into the blood. The bone marrow is typically markedly hypercellular due to the increased numbers of maturing granulocytic precursors. The spleen is also often greatly enlarged as a result of extramedullary hematopoiesis. CML is primarily a disease of adults between the ages 30 and 60. After an average period of 3 years, about half of CML patients enter an accelerated phase of disease, marked by increasing anemia and thrombocytopenia. Within 6 to 12 months, the accelerated phase evolves into a picture that resembles acute leukemia, commonly called a blast crisis. In 70% of blast crises, the blasts are of myeloid origin whereas the remainders are of pre-B cell origin. Understanding the molecular pathogenesis of CML has led to the use of the drug imatinib, which is a specific BCR-ABL inhibitor. Imatinib results in sustained hematologic remission in about 90% of patients with markedly decreased number of BCR-ABL positive cells in the marrow.