TOACS FCPS Station · Chest X‑ray: Mycoplasma Pneumonia (Atypical)

📷 Chest X‑ray (PA view)

Chest X-ray showing bilateral interstitial infiltrates in Mycoplasma pneumonia

Figure 1 · PA chest radiograph · Atypical Pneumonia – Mycoplasma

🔍 Key radiographic features:

✓ Bilateral interstitial infiltrates – reticulonodular pattern
✓ Peribronchial thickening – prominent bronchovascular markings
✓ Patchy consolidation – may be present in lower lobes
✓ No lobar consolidation (unlike typical bacterial pneumonia)
✓ Normal to mild cardiomegaly – no pleural effusion (usually)

📋 Clinical scenario (examiner prompt)

A 12‑year‑old child presents with gradual onset fever, non‑productive cough, and malaise for 1 week. The child appears well despite having a persistent cough and low‑grade fever. On examination, there are bilateral crackles but no signs of respiratory distress. The chest X‑ray (PA view) shows bilateral interstitial infiltrates with peribronchial thickening.

Gradual onset Bilateral interstitial infiltrates Non‑productive cough Walking pneumonia

🧑‍⚕️ Examiner tasks · TOACS

1. Identify the diagnosis from the X‑ray and clinical context.

2. Describe the X‑ray findings (interstitial infiltrates, peribronchial thickening).

3. Explain the pathophysiology (atypical pneumonia, lack of cell wall).

4. Discuss diagnosis and management (PCR, serology, macrolide therapy).

⚠️ Key concept: Mycoplasma pneumoniae is the most common cause of atypical pneumonia in school‑age children and young adults. The chest X‑ray often shows interstitial infiltrates disproportionate to the mild clinical findings (“walking pneumonia”). Macrolides (azithromycin) are first‑line treatment; macrolide resistance is emerging.

🎯 Expected answers (for examiners)

• Diagnosis: Atypical pneumonia (Mycoplasma pneumoniae)
• X‑ray findings: Bilateral interstitial infiltrates, reticulonodular pattern, peribronchial thickening
• Pathophysiology: Smallest free‑living bacterium, lacks cell wall → resistant to beta‑lactams
• Diagnosis: PCR (nasopharyngeal swab) or serology (IgM)
• Management: Azithromycin (10 mg/kg day1, then 5 mg/kg days 2‑5) or clarithromycin

⚡ Quick FCPS‑style MCQ

A 12‑year‑old with fever, non‑productive cough, and bilateral interstitial infiltrates on CXR. The most appropriate treatment is:

A. Amoxicillin B. Azithromycin C. Ceftriaxone D. Vancomycin

📌 Topic summary ·

Organism
Mycoplasma pneumoniae (no cell wall)

Typical CXR
Bilateral interstitial infiltrates

Clinical
Walking pneumonia (CXR > clinical)

First‑line
Macrolides (azithromycin)

Resistance
Macrolide resistance emerging

Alternative
Doxycycline (≥8y) or levofloxacin

Feature	Mycoplasma Pneumonia
CXR pattern	Interstitial infiltrates, reticulonodular
Clinical	Gradual onset, non‑productive cough, malaise
Extrapulmonary	CNS, rash, hemolysis (cold agglutinins)
Diagnosis	PCR (respiratory) or IgM serology
Treatment	Azithromycin or clarithromycin

🩻 TOACS FCPS Station · Chest X‑ray: Atypical Pneumonia (Mycoplasma pneumoniae)

📷 Chest X‑ray (PA view)

🧑‍⚕️ Examiner tasks · TOACS

📌 Topic summary ·