A 70-Year-Old Man With Fever and Fatigue

A 70-year-old previously healthy man presented with fever (highest recorded temperature, 39 °C) and extreme fatigue that had persisted for 2 months. The patient had a slight cough and reported weight loss of 15 kg, but denied the presence of any other symptoms. On initial clinical evaluation, the patient was febrile (temperature, 38.5 °C) and his vital signs were within normal limits. Laboratory investigations revealed progressive pancytopenia, with a white blood cell count of 1.8 × 109/L, hemoglobin of 62 g/L, and a platelet count of 27 × 109/L. The erythrocyte sedimentation rate (56 mm/h) and the level of C-reactive protein (73 mg/L) were elevated. Liver and kidney functions were within the normal range. Blood cultures were negative for aerobic and anaerobic bacteria, mycobacteria, and fungi. Chest computed tomography scanning showed several inflammatory lesions. Abdominal ultrasound showed hepatosplenomegaly (spleen size of 148 mm × 52 mm)...