A 28-year-old woman presents to the emergency department with acute onset dyspnea, chest tightness, and wheezing for the past 2 hours. She has a 10-year history of asthma triggered by dust and pollen. On examination, she is anxious, speaking in short sentences, with bilateral end-expiratory wheezes. Peak expiratory flow (PEF) is 40% of predicted. Chest X-ray shows hyperinflation with normal parenchyma. A sputum sample shows eosinophilia and Curschmann spirals. Which histopathological finding is MOST characteristic of the acute phase of her asthma exacerbation?

Explanation

## Acute Phase Asthma Pathology **Key Point:** The acute asthma exacerbation is characterized by reversible airway obstruction driven by acute inflammatory changes, not structural remodeling. ### Histopathological Features of Acute Asthma | Feature | Acute Phase | Chronic Phase | |---------|-------------|---------------| | **Mucus plugging** | Prominent, eosinophil-rich | Present but less acute | | **Epithelial integrity** | Shedding and denudation | Regenerated but fragile | | **Eosinophil infiltrate** | Abundant (IL-5 driven) | Persistent but lower density | | **Smooth muscle** | Normal or mildly edematous | Hypertrophied and hyperplastic | | **Basement membrane** | Normal thickness | Thickened (>10 μm) | **High-Yield:** Curschmann spirals in sputum are pathognomonic for asthma — they are spiral-shaped mucus plugs formed by the patient's own airway secretions. **Clinical Pearl:** The acute phase is dominated by **reversible** obstruction from mucus, edema, and bronchoconstriction. The chronic phase (remodeling) develops over years and involves smooth muscle hypertrophy, basement membrane thickening, and fibrosis — these are irreversible changes. ### Why Mucus Plugging is the Answer In acute exacerbation: 1. Mast cells and eosinophils degranulate → release IL-5, eotaxin, and mediators 2. Eosinophils infiltrate airway mucosa and submucosa 3. Epithelial cells are damaged and shed, exposing nerve endings 4. Mucus hypersecretion from goblet cell hyperplasia 5. **Result:** Thick, eosinophil-laden mucus plugs occlude small airways → acute airflow obstruction The sputum finding of eosinophilia and Curschmann spirals directly confirms this pathology. **Mnemonic — "ACUTE" asthma:** **A**irway mucus plugging, **C**ontraction (smooth muscle), **U**nderlying eosinophilic infiltrate, **T**emporary (reversible), **E**pithelial shedding.