A thumbprint sign on an X-ray indicates which condition?

• A. Croup
• B. Subglottic swelling
• C. Epiglottitis
• D. Pneumonia

Answer: (C)

The thumbprint sign on a neck radiograph is a classic indicator of epiglottitis. It occurs on a lateral view when the epiglottis becomes swollen and enlarged, taking on a rounded, bulky shape that resembles a thumbprint and sits over the airway. This radiographic appearance highlights the risk of rapid airway obstruction, making it a critical finding in suspected epiglottitis.

In practice, epiglottitis often presents with fever, sore throat, drooling, and the child may assume a tripod or leaning-forward position to ease breathing. By contrast, croup produces a barking cough and typically shows subglottic narrowing on an AP view, known as the steeple sign. Pneumonia would show focal air-space infiltrates rather than an enlarged epiglottis. Subglottic swelling describes edema below the vocal cords but does not create the thumbprint silhouette of the epiglottis.