Cases from the Osler Medical Service at Johns Hopkins University

Presenting features

A 50-year-old Guatemalan man with no significant past medical history was admitted to the Barker Medical Service with weight loss over the past two weeks and fever for two days. His physical examination was remarkable for cachexia. His laboratory studies at presentation were notable for pancytopenia with a white blood cell count of 0.7 × 103/ml, hematocrit of 25% and platelet count of 8000. His admission chest radiography was normal. He had urine and blood cultures sent before beginning broad-spectrum antibiotic coverage with piperacillin/tazobactam and gatifloxacin. His peripheral blood smear is shown in Figure 1. What is the diagnosis?