A previously healthy 13-year-old male presented with a 10-day history of intermittent fevers. He had a several-day history of productive cough with nausea and vomiting and had been treated for dehydration 4 days previously. No chest X-ray was obtained. On the second visit to the ED, the patient was markedly hypotensive (80/40), tachycardic, and febrile at 104.9ºF. On exam, his mentation was slow. The patient’s extremities appeared mottled and cyanotic. He had decreased breath sounds in the left lung fields. Chest X-ray showed left lower lobe pneumonia with a large left pleural effusion (Fig. 1). Laboratory tests showed marked leukocytosis with a left shift. Blood cultures were negative, but nasopharyngeal swabs were positive for influenza A H1 and H3.
The etiology of pneumonia with extensive pleural effusion includes bacteria, with S. pneumoniae, S. aureus and H. influenzae being the most frequent pathogens, followed by viral agents, atypical bacteria, and, rarely, malignancy. Influenza A and RSV are the most common causes of viral pneumonia, followed by adenovirus, parainfluenza virus, and influenza B . Pneumonia occurs in a minority of patients with influenza (3–16%) . Pleural effusion, while likely to develop in at least 40% of patients with bacterial pneumonias , is a rare complication of influenza pneumonia . Bacterial coinfection is the most common complication of influenza pneumonia and occurs in up to 20% of cases . This child had a high probability of having a bacterial coinfection. His late presentation precluded treatment with adamantanes or neuraminidase inhibitors.