Psittacosis pneumonia with the reversed halo sign: a case report and literature review.

Background: Chlamydia psittaci is a rare pathogen that causes community-acquired pneumonia. The reversed halo sign (RHS) is a computed tomography (CT) finding that is commonly observed in diseases such as cryptogenic organizing pneumonia, invasive fungal infections, tuberculosis, sarcoidosis, and pulmonary thromboembolism, but has seldom been described in association with psittacosis pneumonia.

Case presentation: We report a case in which a 26-year-old man with a history of close contact with pigeons and chicken manure presented with fever and cough for 6 days. A CT examination revealed the RHS in the right lower lobe of the lung. Psittacosis pneumonia was diagnosed by metagenomic next-generation sequencing of the patient's bronchoalveolar lavage fluid. Treatment with omadacycline abolished his symptoms. We also discuss six other cases of psittacosis pneumonia with the RHS identified by literature search.

Conclusions: When clinicians encounter patients with atypical pneumonia with the RHS and a history of contact with poultry, psittacosis should be considered.