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Difficulty: MediumPediatric Infectious Diseases

A 9-year-old girl is brought to the outpatient pediatric clinic by her father due to a persistent cough that has worsened over the past 14 days. The cough is dry, hacking, and most prominent at night. She also reports mild fatigue, a low-grade fever, and a dull headache. She has no history of asthma or environmental allergies, and her immunizations are up to date. Vital signs show a temperature of 37.9°C (100.2°F), heart rate of 98/min, respiratory rate of 22/min, and oxygen saturation of 98% on room air. She appears comfortable and is in no acute distress. Lung auscultation reveals faint bilateral wheezes and scattered fine crackles. A chest radiograph demonstrates diffuse, patchy interstitial infiltrates. Which of the following is the most appropriate next step in management?

  1. A
    Administer intravenous ceftriaxone and admit for observation
  2. B
    Prescribe oral amoxicillin-clavulanate
  3. Prescribe oral azithromycinAnswer
  4. D
    Initiate nebulized albuterol and oral dexamethasone
  5. E
    Prescribe oral ciprofloxacin

Answer

Prescribe oral azithromycin
The correct answer is to prescribe oral azithromycin. This patient's clinical presentation—a subacute, prolonged dry cough, low-grade fever, headache, and fatigue in a school-aged child—is classic for atypical pneumonia. The chest radiograph showing diffuse, patchy interstitial infiltrates (often appearing worse than the patient's clinical state) further supports this diagnosis. In children aged 5 years and older, Mycoplasma pneumoniae is the most common bacterial cause of community-acquired pneumonia. Because Mycoplasma species lack a peptidoglycan cell wall, they are intrinsically resistant to beta-lactam antibiotics (e.g., penicillins, cephalosporins). Macrolide antibiotics, such as azithromycin, target bacterial protein synthesis by binding to the 50S ribosomal subunit and represent the first-line empiric treatment for outpatient atypical pneumonia in this age group.

Step-by-Step Solution

1
Analyze the clinical presentation and patient demographics.
A 9-year-old child presents with a subacute onset of dry cough, low-grade fever, headache, and malaise over 2 weeks.
Identifying the age group and symptom timeline helps differentiate typical from atypical respiratory infections.
2
Evaluate the physical examination and radiographic findings.
The patient is well-appearing but has bilateral wheezes/crackles and diffuse interstitial infiltrates on chest X-ray.
These findings classically point to 'walking pneumonia' (atypical pneumonia) rather than a focal lobar consolidation seen in typical bacterial pneumonia.
3
Identify the most likely causative organism.
Mycoplasma pneumoniae is the most common cause of atypical pneumonia in school-aged children and adolescents.
Recognizing the pathogen dictates the appropriate targeted antimicrobial therapy.
4
Select the appropriate pharmacotherapy.
Oral azithromycin is selected.
Mycoplasma lacks a cell wall, rendering beta-lactams ineffective. Macrolides are the first-line treatment of choice.

Key Concept

Diagnosis and management of atypical community-acquired pneumonia in school-aged children.
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Topics

Pediatric Infectious Diseases

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