Clinical reasoning: a 69-year-old man with leukocytosis and hemorrhagic brain lesions.

SECTION 1 A 69-year-old man was admitted to our hospital with left upper quadrant pain, splenomegaly, acute renal failure, hyperuricemia, thrombocytopenia (platelet count 32,000/mm), and leukocytosis (leukocyte count 88,000/mm). His medical history was significant for prior diagnosis of myelodysplastic syndrome (MDS) by bone marrow biopsy at an outside institution treated with the hypomethylating chemotherapeutic agent decitabine, atrial fibrillation, cardiomyopathy, and complete pacemaker dependence. Neurologic examination upon admission was normal. The initial diagnostic considerations were tumor lysis syndrome from decitabine treatment vs transformation of MDS to acute myeloid leukemia (AML). Treatment with hydroxyurea and leukapheresis was initiated to reduce the leukocyte count, which reached a peak of 104,000/mm during hospitalization. Three days after admission, the patient developed dysarthria and double vision, which prompted neurologic consultation. The neurologic examination was remarkable for esotropia OS, impaired abduction OS, impaired adduction OD, and moderate dysarthria without aphasia. Mental status, visual acuity, sensation, facial and limb motor function, reflexes, and coordination were normal.