A 5-week-old full-term infant presents with a repetitive staccato cough and tachypnoea for 10 days. He is afebrile and feeding adequately. Chest X-ray shows bilateral diffuse interstitial infiltrates. Total leucocyte count is normal with 18% eosinophils. He was treated for bilateral watery eye discharge at 2 weeks of age. Which investigation will best confirm the diagnosis?

• A Blood culture on MacConkey agar
• B Serum IgE level alone
• C Sputum Ziehl-Neelsen stain
• D Nucleic acid amplification test on nasopharyngeal aspirate for Chlamydia trachomatis ✓

Explanation

Infantile chlamydial pneumonia occurs between 3 weeks and 3 months of age and classically presents as an afebrile illness with a staccato cough, bilateral interstitial infiltrates, and peripheral eosinophilia. A history of neonatal chlamydial conjunctivitis strongly supports the diagnosis. Confirmation rests on detecting Chlamydia trachomatis in respiratory secretions by nucleic acid amplification testing or direct fluorescent antibody staining. The absence of fever distinguishes it from bacterial and most viral pneumonias in this age group.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.