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Difficulty: Very hardPediatric Respiratory Disorders

A 6-week-old boy is brought to the pediatrician by his mother due to a 7-day history of a worsening, repetitive cough. The mother describes the cough as occurring in rapid, short bursts, occasionally causing the infant's face to turn red, though without a distinct "whoop" sound or post-tussive emesis. The infant is exclusively breastfed and has been afebrile. He received his first hepatitis B vaccination at birth and is not yet due for his 2-month immunizations. Medical history is notable for bilateral mucopurulent eye discharge at 10 days of life, which resolved after a 7-day course of topical erythromycin ointment.

Vital signs are temperature 37.1°C (98.8°F), heart rate 145/min, respiratory rate 58/min, and oxygen saturation 95% on room air. Lung auscultation reveals bilateral scattered crackles and occasional expiratory wheezes without prominent intercostal retractions.

Laboratory testing shows a leukocyte count of 14,500/mm314,500/\text{mm}^3 with 35%35\% neutrophils, 45%45\% lymphocytes, and 15%15\% eosinophils. A chest radiograph demonstrates bilateral symmetric interstitial infiltrates and hyperinflation.

Which of the following is the most appropriate next step in the management of this patient?

  1. Oral azithromycinAnswer
  2. B
    Supportive care with nasal suctioning and hydration
  3. C
    Nebulized albuterol and oral dexamethasone
  4. D
    Intravenous ceftriaxone
  5. E
    Oral amoxicillin

Answer

Oral azithromycin
The correct intervention is oral azithromycin. The patient's presentation of an afebrile, "staccato" (short, repetitive) cough at 6 weeks of age, accompanied by peripheral eosinophilia and a history of neonatal conjunctivitis, is highly characteristic of Chlamydia trachomatis pneumonia. Importantly, while topical erythromycin successfully treats the local ophthalmic symptoms of chlamydial conjunctivitis, it fails to eradicate the nasopharyngeal colonization. This allows the infection to progress to pneumonia, typically manifesting between 4 and 12 weeks of life. The treatment of choice for infantile chlamydial pneumonia is a systemic macrolide, such as oral azithromycin, which effectively targets this intracellular organism.

Step-by-Step Solution

1
Analyze the clinical presentation, focusing on the infant's age, symptom quality, and vital signs.
A 6-week-old afebrile infant presenting with a staccato cough, wheezing, and hyperinflation.
Establishing the core clinical syndrome helps narrow the differential diagnosis of neonatal and early infant respiratory distress.
2
Synthesize the laboratory findings and past medical history with the clinical picture.
The presence of 15% eosinophilia and a history of conjunctivitis treated only with topical antibiotics strongly suggest Chlamydia trachomatis.
Topical antibiotics do not eradicate nasopharyngeal chlamydial carriage, leading to pneumonia weeks later, which classically features prominent eosinophilia.
3
Determine the optimal pharmacological intervention for the identified pathogen.
A systemic macrolide is required.
Chlamydia is an intracellular organism lacking a classic cell wall, making beta-lactams ineffective; systemic macrolides like oral azithromycin are the treatment of choice.

Key Concept

Diagnosis and treatment of infantile Chlamydia trachomatis pneumonia, characterized by an afebrile staccato cough, eosinophilia, and a history of inadequately treated neonatal conjunctivitis.
Estimated Time:1m 30s
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Topics

Pediatric Respiratory Disorders

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