Clinical meaning
Eosinophilic pneumonia is characterized by massive eosinophil accumulation in the alveoli and interstitium driven by IL-5 and eotaxin-mediated chemotaxis. Eosinophils release cytotoxic granule proteins (major basic protein, eosinophil peroxidase) that directly damage alveolar epithelial cells and basement membranes. Acute eosinophilic pneumonia (AEP) presents with rapid-onset respiratory failure, often in new smokers or after environmental exposure. Chronic eosinophilic pneumonia (CEP) follows a more indolent course with characteristic peripheral pulmonary infiltrates (photographic negative of pulmonary edema).
Exam relevance
Risk factors: - New-onset cigarette smoking or recent change in smoking habits (AEP) - Environmental dust or smoke exposure - Drug reactions (NSAIDs, sulfonamides, nitrofurantoin) - Parasitic infections (Ascaris, Strongyloides) - Atopic history (asthma, allergic rhinitis) - History of prior eosinophilic disease
Diagnostics: - CBC with differential showing peripheral eosinophilia (may be absent in AEP) - BAL showing eosinophils > 25% (diagnostic) - CT chest: peripheral consolidations (CEP) or diffuse ground-glass (AEP) - IgE level often elevated - Stool ova and parasites to rule out parasitic cause - Pulmonary function tests (restrictive or obstructive pattern)