Key Concepts
Introduction
Radiation pneumonitis develops 1-6 months after thoracic irradiation when ionizing radiation damages type I and type II pneumocytes and pulmonary capillary endothelial cells. Free radical-mediated DNA damage triggers apoptosis of alveolar lining cells, leading to surfactant depletion, increased capillary permeability, and alveolar edema. The inflammatory response involves macrophage and lymphocyte infiltration with release of pro-fibrotic cytokines (TGF-beta, TNF-alpha). Without treatment, the acute inflammatory phase progresses to irreversible radiation fibrosis within 6-24 months. On the exam, writers often pair stable-sounding options with unstable dataโnotice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that reduces imminent harm and matches orders for the role you were given. Train yourself to state the primary risk in one short phrase before you read the options so distractors do not rewrite your priority...