Radiation exposure within less than 12 weeks commonly leads to which condition?

• A. Pneumonitis
• B. Pneumoconiosis
• C. Pulmonary fibrosis
• D. Hypersensitivity pneumonitis

Answer: (A)

Radiation injury to the lungs tends to provoke an early inflammatory reaction in the irradiated parenchyma. This acute inflammatory response is called radiation pneumonitis and it typically appears within weeks to a few months after exposure to thoracic radiation, often within 12 weeks. The process involves inflammatory edema and cellular infiltration of the lung tissue in the affected area, leading to symptoms like cough and shortness of breath, and it may show patchy opacities on imaging in the irradiated field.

Pneumoconiosis results from long-term inhalation of mineral dust and develops slowly over years, not within a short post-exposure period. Pulmonary fibrosis is a broader term for scarring of the lung and can be a later consequence of radiation, but the immediate, timeframe-based reaction within 12 weeks is the pneumonitis phase. Hypersensitivity pneumonitis is an immune-mediated reaction to inhaled antigens and is not specifically linked to recent radiation exposure.