Which radiographic sign is classic for croup and helps differentiate it from other upper airway infections?

• A. Steeple Sign
• B. Thumbprint Sign
• C. Pill Sign
• D. Cord Sign

Answer: (A)

The key concept is recognizing how croup alters the upper airway on imaging. In viral croup, inflammation and edema concentrate in the subglottic portion of the trachea, narrowing the airway just below the vocal cords. On an AP neck radiograph this narrowing creates a tapered, church-spire-like silhouette—the steeple sign. That steeple appearance is the classic radiographic clue that helps differentiate croup from other upper airway infections, such as epiglottitis, where a lateral view would show the thumbprint sign (edematous epiglottis). The other signs mentioned aren’t characteristic indicators of croup, so they don’t provide the same diagnostic cue. In practice, imaging supports the clinical picture, with the steeple sign serving as the distinguishing radiographic feature for croup.