Clinical and CT diagnosis of 50 cases of Chlamydia psittaci pneumonia

This is a retrospective cross-sectional study aiming to explore the clinical and imaging manifestations of Chlamydia psittaci pneumonia (CPP), thus improving its diagnosis, guiding its early clinical treatment, and reducing its mortality rate.

Fifty cases of CPP diagnosed by hospitals across the country with metagenomics next-generation sequencing (mNGS) from January 2019 to March 2021 were collected. Its clinical symptoms, laboratory test results, and computed tomography (CT) features were discussed.

Forty patients had a history of poultry exposure; 37 experienced respiratory symptoms, 48 had a fever, 14 experienced gastrointestinal symptoms, and 12 experienced neurological symptoms; 34 patients had normal blood cell counts, 49 patients had elevated C-reactive protein, and 24 showed decreased serum sodium. Imaging manifestations: (I) Distribution: lesions were limited to a single lung in 31 patients, lesions were distributed in bilateral lungs in 19 patients; (II) Signs: 37 patients developed the "fine mesh sign". Necrosis, cavity and "tree-in-bud" were not observed. Pleural effusion occurred in 33 patients, mediastinal lymphadenopathy in 18, and splenomegaly in 15 patients.

Patients with CPP often have a history of poultry exposure and present with fever and increased C-reactive protein. White blood cells may be slightly increased or completely normal. Hyponatremia may occur in some patients, and multiple systems may be clinically involved. The imaging can show lesions with unilateral or bilateral lung distribution and a rapid progression. Both the lung parenchyma and the interstitium are involved. Fine mesh sign is the most common sign. Necrosis, cavitation, and tree-in-bud signs are not observed. In conclusion, imaging examinations are helpful for the early diagnosis of this disease and the evaluation of the treatment effect.