# Unusual Air Crescents on Chest Radiographs

## TL;DR

This paper presents four rare causes of air crescents seen on chest X-rays that have not been previously reported in medical literature.

## Contribution

The study introduces four uncommon, previously undocumented causes of air crescent signs on chest radiographs.

## Key findings

- Oesophageal bezoar can present as an air crescent sign on chest radiographs.
- Interstitial lung emphysema is another rare cause of air crescents.
- Central bronchial stenosis and perforated emphysematous cholecystitis were also identified as unusual causes.

## Abstract

The air crescent (AC) is a common radiological sign. Even if its commonest aetiology remains pulmonary aspergillosis, various other causes have been described. In this study, we report four rare causes of ACs seen on chest radiographs that haven’t been described in the literature.

Teaching point: The differential diagnosis of an air crescent sign on chest radiographs includes oesophageal bezoar, interstitial lung emphysema, central bronchial stenosis and perforated emphysematous cholecystitis.