A 3-year-old boy is brought to the emergency department after a sudden coughing fit while eating peanuts. His mother states he was fine one moment and then began gasping for air. Past medical history is negative. Vital signs show he is afebrile with an elevated heart rate and elevated respiratory rate. On physical examination, he is tachypneic and appears anxious. Lung auscultation reveals decreased breath sounds and localized expiratory wheezing on the right side. There is no fever, drooling, or muffled voice.
Which of the following is the most likely diagnosis?
The correct answer is:
C) Foreign body aspiration
Foreign body aspiration is a common cause of sudden-onset respiratory distress in toddlers. The classic presentation involves a sudden episode of choking and coughing in a previously healthy child. When a foreign body enters the lower airway, it most commonly lodges in the right main bronchus because it is wider, shorter, and more vertical than the left. This leads to unilateral physical findings, such as localized wheezing or diminished breath sounds. If the object creates a ball-valve effect, air can enter but not exit, leading to hyperinflation of the affected lung seen on chest X-ray.
Answer choice A: Acute epiglottitis, is incorrect. While epiglottitis causes obstruction, it is a supraglottic infection characterized by high fever, drooling, and inspiratory stridor, not localized wheezing.
Answer choice B: Croup (laryngotracheobronchitis), is incorrect. Croup presents with a gradual onset of upper respiratory infection (URI) symptoms followed by a barking cough and inspiratory stridor. It is caused by subglottic swelling and would show bilateral findings or the steeple sign on X-ray of the neck.
Answer choice D: Laryngeal edema, is incorrect. Laryngeal edema typically presents with rapidly progressive stridor and is usually associated with an allergic trigger (anaphylaxis) or trauma.
Answer choice E: Retropharyngeal abscess, is incorrect. Retropharyngeal abscess presents with fever, muffled voice, and neck stiffness, usually developing over days rather than seconds.
Key Learning Point
Identifying the level of obstruction is key for the USMLE. Inspiratory stridor indicates an upper airway obstruction above or at the vocal cords, such as epiglottitis, croup, or laryngomalacia. Expiratory wheezing indicates a lower airway obstruction below the carina, such as asthma or a foreign body in a bronchus. Biphasic stridor indicates a subglottic or tracheal narrowing such as tracheal stenosis.
