A 68-year-old man with chronic obstructive pulmonary disease presents with a 3-day history of productive cough with purulent sputum, fever (38.5°C), and dyspnea. Chest X-ray shows patchy infiltrates in the right lower lobe and left lower lobe with a "tree-in-bud" appearance. Sputum culture grows Haemophilus influenzae. Which pathological pattern of pneumonia is most consistent with this clinical and radiological presentation?

Explanation

## Diagnosis: Bronchopneumonia ### Clinical and Radiological Clues **Key Point:** The patchy, multifocal distribution of infiltrates with a "tree-in-bud" pattern is pathognomonic for bronchopneumonia, not lobar consolidation. **High-Yield:** Bronchopneumonia characteristically affects: - Multiple lobes (bilateral lower lobes in this case) - Peribronchial regions (hence "tree-in-bud" on HRCT) - Patients with underlying lung disease (COPD here) - Gram-negative organisms like *Haemophilus influenzae* and *Pseudomonas* ### Pathological Comparison: Lobar vs Bronchopneumonia | Feature | Lobar Pneumonia | Bronchopneumonia | |---------|-----------------|------------------| | **Distribution** | Entire lobe or segment | Patchy, multifocal | | **Typical CXR** | Homogeneous consolidation, air bronchogram | Patchy infiltrates, tree-in-bud | | **Lobes affected** | Usually single lobe | Multiple lobes, bilateral common | | **Common organisms** | *Streptococcus pneumoniae*, *Legionella* | *H. influenzae*, *Staph aureus*, Gram-negatives | | **Risk factors** | Healthy young/middle-aged | COPD, elderly, aspiration, immunocompromised | | **Consolidation pattern** | Acute inflammatory edema → red hepatization → gray hepatization | Suppurative inflammation in bronchi and alveoli | ### Why This Patient Has Bronchopneumonia 1. **Underlying COPD** — predisposes to bronchopneumonia, not lobar pneumonia 2. **Patchy bilateral infiltrates** — classic bronchopneumonia pattern; lobar pneumonia would show homogeneous consolidation of one lobe 3. **"Tree-in-bud" appearance** — indicates peribronchial inflammation and small airway involvement 4. **Organism: *H. influenzae*** — common in COPD exacerbations with bronchopneumonia; *S. pneumoniae* is the classic lobar pneumonia organism **Clinical Pearl:** Lobar pneumonia typically presents acutely in previously healthy individuals with sudden onset and high fever; bronchopneumonia is more insidious, often in patients with chronic lung disease or immunosuppression. ### Pathological Mechanism Bronchopneumonia begins in the terminal and respiratory bronchioles, with inflammation spreading centrifugally. Consolidation is patchy and multifocal. Lobar pneumonia, by contrast, spreads centripetally from the pleura inward, affecting an entire anatomical lobe uniformly.