A 50-year-old coalmine worker develops progressive massive fibrosis on CXR. Biopsy shows silicotic nodules with concentric whorls of collagen fibers with a necrotic center. The central necrosis in these nodules is caused by:

• A Superimposed bacterial infection
• B Ischemia from vascular obliteration
• C Hypersensitivity reaction to coal dust
• D Superimposed Mycobacterium tuberculosis coinfection ✓

Explanation

Progressive massive fibrosis in coal workers' pneumoconiosis and silicosis can develop central necrosis when silicotic nodules become infected with Mycobacterium tuberculosis, a known complication called silicotuberculosis. Silica is directly toxic to alveolar macrophages and impairs their ability to kill mycobacteria after phagocytosis, greatly increasing susceptibility to tuberculosis. Pure silicotic nodule necrosis without TB is less common and usually attributed to ischemia.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.