A 47-year-old pigeon breeder has four months of episodic breathlessness that worsens at home. HRCT shows diffuse centrilobular ground-glass nodules with patchy air trapping on expiratory sequences and a three-density pattern. BAL shows marked lymphocytosis. Which organism or antigen class is the classic cause when the same picture follows stored mouldy hay exposure?
- A Thermophilic actinomycetes such as Saccharopolyspora rectivirgula ✓
- B Avian serum proteins present in feather dust
- C Mycobacterium avium complex from hot tub aerosols
- D Aspergillus fumigatus in an atopic host
Correct answer: A. Thermophilic actinomycetes such as Saccharopolyspora rectivirgula
Explanation
Farmer's lung is caused by inhalation of thermophilic actinomycetes, classically Saccharopolyspora rectivirgula (formerly Micropolyspora faeni), growing in mouldy hay. Avian proteins cause bird fancier's disease, MAC causes hot tub lung, and Aspergillus fumigatus causes allergic bronchopulmonary aspergillosis, a Th2 eosinophilic disorder rather than a granulomatous hypersensitivity pneumonitis. The HRCT findings described are typical of nonfibrotic hypersensitivity pneumonitis regardless of antigen.
Reference: Fishman's Pulmonary Diseases and Disorders, 5th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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