A 10-month-old infant presents in winter with wheezing, tachypnea, and subcostal retractions for the first time. He has no prior history of asthma or atopy. On examination, there is prolonged expiration with widespread crepitations. Chest X-ray shows hyperinflation. What is the most likely diagnosis?

• A Bronchial asthma
• B Foreign body aspiration
• C Acute bronchiolitis ✓
• D Pertussis

Explanation

Acute bronchiolitis is the most common lower respiratory tract infection in infants under 2 years, predominantly caused by Respiratory Syncytial Virus (RSV). It classically occurs in winter epidemics with a first episode of wheeze in a young infant, characterized by tachypnea, subcostal retractions, prolonged expiration, crepitations, and hyperinflation on chest X-ray. It is distinguished from asthma (which is recurrent and rare under 2 years) and foreign body aspiration (sudden onset, no fever). Treatment is supportive.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.