A 45-Year-Old Man with Cough and a Cavitary Lung Lesion

45-year-old man with no significant medical history was admitted to hospital with a four-month history of intermittent fever and a predominantly dry cough. Approximately one month before admission, he started developing worsening cough with scant expectoration and pleuritic left-sided chest pain. His symptoms persisted and he presented for admission. On examination, the patient appeared chronically ill and nontoxic. His vital signs were stable except for mild tachycardia, with a heart rate in the low one hundreds. Examination of the mouth revealed him to be partially edentulous with poor orodental hygiene, although there was no evidence of dental abscesses. A chest examination revealed diminished breath sounds to the left infraaxillary area. His laboratory results were significant for mild leukocytosis (white blood cell count 13×10 9 /L) and mild anemia (hemoglobin level 90 g/L). Kidney and liver function tests were within normal limits. A chest radiograph showed a left perihilar infiltrate. An axial computed tomography (CT) scan of the chest showed a patchy infiltrate to the posterior upper lung with a central air cavity measuring 2.9 cm × 0.7 cm and a small left-sided pleural effusion (Figure 1). The patient was placed on moxifloxacin and clindamycin and a procedure was performed. What is your diagnosis? Diagnosis The patient did not improve clinically after 10 days of antibiotic therapy and was taken to the operating room for an open left thoracotomy with decortication and drainage of the empyema. The Gram stain of the pleural fluid culture showed branching, Gram-positive rods (Figure 2) and cultures yielded Actinomyces meyeri. The patient’s antibiotic regimen was switched to intravenous penicillin, three million units every 4 h. He was treated with intravenous penicillin for a twoweek course in the hospital and was discharged home to complete a 12-month course of oral penicillin, 500 mg every 6 h. Discussion