# Clinical features and chest CT findings of Chlamydia pneumoniae pneumonia

## TL;DR

This study describes the clinical symptoms and chest CT patterns in patients with Chlamydia pneumoniae pneumonia, highlighting key imaging features that could aid in early diagnosis.

## Contribution

The study identifies specific chest CT imaging patterns and clinical features unique to Chlamydia pneumoniae pneumonia, including potential early markers for clinical intervention.

## Key findings

- Chest CT findings in Chlamydia pneumoniae pneumonia include lobular pneumonia patterns, lower-lobe distribution, and features like bronchial wall thickening and centrilobular nodules.
- Early-stage imaging features include a nodular-patchy pattern, which may serve as an ultra-early marker for the disease.
- Clinical symptoms such as fever, cough, and elevated C-reactive protein levels are common in affected patients.

## Abstract

This study aimed to investigate the clinical features and chest computed tomography (CT) findings in 42 patients with Chlamydia pneumoniae pneumonia, as confirmed by metagenomic next-generation sequencing (mNGS).

We conducted a retrospective analysis of clinical data and chest CT findings (both at disease onset and within 1 month thereafter) in 42 patients diagnosed with Chlamydia pneumoniae pneumonia by mNGS at our hospital between August 2022 and August 2025.

Of the 42 patients, 25 (59.5%) presented with fever, 26 (61.9%) with sore throat, 30 (71.4%) with cough, 27 (64.3%) with expectoration, 11 (26.2%) with myalgia, 10 (23.8%) with general fatigue, and 10 (23.8%) with neurological symptoms such as headache and dizziness. Laboratory tests revealed that 12 patients (28.6%) showed a mild increase in white blood cell count, 10 (23.8%) had elevated neutrophil counts, 21 (50.0%) exhibited elevated C-reactive protein (CRP) levels, and 6 (14.3%) had CRP levels exceeding 100 mg/L. In the early stage, chest CT demonstrated a lobular pneumonia pattern in 16 patients (55.2%), involvement of a single lung lobe in 20 (69.0%), predominant lower-lung distribution in 19 (65.5%), and a nodular-patchy pattern in 8 patients (27.6%) with a nodular–patchy pattern. The main accompanying features included a halo sign in 25 patients (86.2%), centrilobular nodules in 23 (79.3%), and bronchial wall thickening in 20 (69.0%). In the mid-to-late stage, chest CT revealed a lobular pneumonia pattern in 23 patients (76.7%), single-lobe involvement in 23 (76.7%), and predominant lower-lung distribution in 20 (66.7%). The major concomitant features were a halo sign in 21 patients (70.0%), centrilobular nodules in 20 (66.7%), and bronchial wall thickening in 24 (80.0%).

Chest CT findings of Chlamydia pneumoniae pneumonia are predominantly characterized by a lobular pneumonia pattern, lower-lobe distribution, and associated features such as bronchial wall thickening, centrilobular nodules, and a peripheral halo sign. Certain imaging differences exist between early and middle-to-late stages, with the nodular-patchy pattern potentially representing an ultra-early imaging marker, which may provide clues for early clinical intervention.