Which condition is indicated by the steeple sign on an X-ray?

The steeple sign observed on an X-ray is indicative of croup, which is also known as laryngotracheobronchitis. This sign refers to the characteristic narrowing of the upper airway, specifically in the area of the subglottic region, which appears to be shaped like a steeple or a church spire on imaging. This narrowing is often a result of inflammation and edema associated with viral infections, most commonly the parainfluenza virus.

In croup, patients typically present with a distinctive barky cough, stridor (a high-pitched sound during breathing), and hoarseness. These symptoms, combined with the steeple sign seen on the X-ray, provide a clear indication of the diagnosis. The other conditions listed do not produce this specific X-ray finding and have different clinical presentations. For example, bronchiolitis primarily affects the lower airways and does not typically present with the steeple sign. Pneumonia may show consolidation or other patterns on X-ray but not the characteristic narrowing seen in croup. Similarly, epiglottitis presents with different X-ray findings, such as the "thumb sign," indicating swelling of the epiglottis rather than the subglottic