Abstract
Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disorder characterized by the presence of the Philadelphia chromosome, t(9;22), which is a constitutively active tyrosine kinase that causes excessive proliferation and differentiation of myeloid cells in the bone marrow. Most patients are either asymptomatic or present with fatigue, abdominal fullness, and splenomegaly. This is a case in which a 72-year-old Caucasian male's initial presentation of CML was new-onset atrial fibrillation, chronic obstructive pulmonary disease (COPD) exacerbation, and pneumonia. The severity of his symptoms of atrial fibrillation and dyspnea complicated his stabilization, which delayed his diagnosis of CML and initiation of tyrosine kinase inhibitor for treatment. Unregulated proliferation of leukemic cells increases blood viscosity and results in aberrations in blood circulation that may result in atypical presenting symptoms in myeloproliferative disease. Thus, it is important to have a high clinical index of suspicion for CML in patients with leukocytosis and concurrent symptomatology that is unusual for leukemia.