Review Question - QID 106609

CML is caused by neoplastic transformation of bone marrow stem cells that are still able to differentiate to fully mature cells.

CML is caused by a balanced translocation of chromosome 9 and 22 resulting in a Philadelphia chromosome (BCR-ABL 1 fusion gene). Typically, the disease presents in adults less than 50 years of age. Some patients present with unexplained constitutional symptoms or splenomegaly, but 20% of patients are asymptomatic.

Davis et al. explain that the diagnosis of CML requires cytogenetic testing for the Philadelphia chromosome, found in 95% of CML cases. Cytogenetic testing involves examination of whole chromosomes through karyotyping or fluorescence in situ hybridization (FISH) analysis.

Moen et al. discuss the use of imatinib (Gleevac), a tyrosine kinase inhibitor as a treatment for CML. It is specifically engineered to inhibit the breakpoint cluster region of the BCR-ABL fusion protein. It is useful in all stages of the disease, but especially as initial treatment of newly diagnosed Philadelphia chromosome positive chronic-phase CML.

Figure A shows a peripheral blood smear with marked leukocytosis with granulocyte left shift. Myeloid cells become either monocytes or granulocytes. Illustration 1 demonstrates an evaluation algorithm for suspected leukemias (ALL, AML, CLL and CML).

Incorrect Answers
Answer 1: ALL typically affects children, and blast cells are seen on peripheral blood smear or bone marrow aspirate.
Answer 2: AML typically affects adults, and blast cells are seen on peripheral smear or bone marrow aspirate. Auer rods may also be seen on peripheral smear.
Answer 3: CLL typically affects older adults and is characterized by a clonal expansion of lymphocytes in the peripheral blood.
Answer 5: APL is the M3 subtype of AML is a result of abnormal accumulation of immature granulocytes (promyelocytes) and is characterized by a chromosomal translocation of retinoic acid receptor alpha.