A 72-year-old woman with chronic obstructive pulmonary disease (COPD) presents with a 10-day history of progressive cough, low-grade fever (37.8°C), and dyspnea. Chest X-ray shows scattered, ill-defined infiltrates predominantly in the lower lobes bilaterally, with a peribronchial distribution. Sputum culture grows Haemophilus influenzae. Which pathological pattern best describes this pneumonia?

Explanation

## Diagnosis: Bronchopneumonia ### Clinical Presentation Analysis **Key Point:** The insidious onset, patchy bilateral lower lobe infiltrates with peribronchial distribution, and H. influenzae isolation are diagnostic of bronchopneumonia. ### Pathological Distinction: Lobar vs Bronchopneumonia | Feature | Lobar Pneumonia | Bronchopneumonia | |---------|-----------------|------------------| | **Onset** | Sudden (hours) | Insidious (days) | | **Distribution** | Single lobe/segment | Patchy, multifocal, bilateral | | **Radiological pattern** | Homogeneous consolidation + air bronchograms | Peribronchial infiltrates, scattered foci | | **Pathological focus** | Alveolar filling (centripetal spread) | Bronchial inflammation (centrifugal spread) | | **Common organisms** | S. pneumoniae, S. pyogenes | H. influenzae, S. aureus, Gram-negatives, anaerobes | | **Risk factors** | Healthy individuals, acute illness | COPD, elderly, immunocompromised, aspiration | | **Pleural involvement** | Fibrinous pleuritis common | Rare | | **Recovery** | Rapid defervescence ("crisis") | Gradual, lytic | ### Why This Is Bronchopneumonia 1. **Insidious onset:** 10-day progressive course (not acute) 2. **Radiological distribution:** Patchy, scattered infiltrates with peribronchial pattern — hallmark of bronchopneumonia 3. **Bilateral involvement:** Lower lobes bilaterally (not confined to single lobe) 4. **Organism:** H. influenzae is a classic bronchopneumonia pathogen, especially in COPD 5. **Risk factor:** COPD predisposes to bronchopneumonia, not lobar pneumonia 6. **Low-grade fever:** Gradual systemic response typical of bronchopneumonia **High-Yield:** Bronchopneumonia is **bronchocentric** — inflammation begins in bronchi and spreads centrifugally to surrounding alveoli. Lobar pneumonia is **alveolar-centric** — starts in alveoli and spreads centripetally. **Clinical Pearl:** In elderly and COPD patients, bronchopneumonia is far more common than lobar pneumonia. The peribronchial distribution on imaging is the key radiological clue. ### Pathological Mechanism: Bronchopneumonia ```mermaid flowchart TD A[Aspiration or Inhalation of Organisms]:::action --> B[Colonization of Bronchi]:::outcome B --> C[Bronchitis with Purulent Exudate]:::outcome C --> D[Centrifugal Spread to Adjacent Alveoli]:::action D --> E[Patchy Alveolar Consolidation<br/>Around Bronchi]:::outcome E --> F[Multifocal, Scattered Pattern<br/>Often Bilateral]:::outcome F --> G[Gradual Resolution<br/>over 2-3 weeks]:::action ``` **Key Point:** The inflammation originates in the bronchi and spreads outward, creating a peribronchial distribution — the opposite of lobar pneumonia's centripetal pattern.