Snapshot A 62-year-old man presents to his primary care provider for an urgent care visit. He reports feeling very fatigued recently. He denies any change in bowel movements or any blood in his stool. On physical exam, he has mild splenomegaly. Blood tests come back with increased leukocytosis with neutrophilic dominance and increased basophils. Concerned, his primary care provider refers him to hematology-oncology. His peripheral smear shows myeloid cells. Introduction Also known as chronic myelogenous leukemia Clonal hematopoietic stem cell disorder Pathogenesis Philadelphia chromosome translocation t(9;22) BCR-ABL fusion gene hyperactive tyrosine kinase Epidemiology median disease onset 67 years of age 15% of all adult leukemias May transform into blast crisis AML or ALL Presentation Symptoms B symptoms (fever, weight loss, fatigue) splenomegaly LUQ discomfort early satiety Physical exam splenomegaly common Evaluation Complete blood count with differential ↑ WBC ↑ neutrophils ↑ basophils ↑ metamyelocytes ↓ leukocyte alkaline phosphatase low activity in mature granulocytes Bone marrow aspirate and biopsy Cytogenetic analysis or FISH showing Philadelphia chromosome (most accurate) Differential Diagnosis Chronic myelomonocytic leukemia Chronic eosinophilic leukemia Primary myelofibrosis Acute myeloid leukemic Leukemoid reaction ↑ WBC ↑ leukocyte alkaline phosphatase Treatment Medical management tyrosine kinase inhibitors are first-line imatinib (Gleevec) nilotinib dasatinib Surgical management hematopoietic stem cell transplant never first-line the only curative therapy Prognosis, Prevention, and Complications Prognosis worse prognosis with older age at diagnosis increased overall survival with tyrosine kinase inhibitor therapy Complications transformation to acute leukemia (blast crisis) infection bleeding bone pain splenic infarcts due to splenomegaly