Q: 23 year old male presented to ER with shortness of breath. Patient history is significant with mediastinal mass and had radiation and chemotherapy 2 months ago. Following is the CXR. What is your probable diagnosis?

Answer: Radiation Pneumonitis

Radiation Pneumonitis occurs at dose beyond 4500 rads and is likely to happen if dose  >6000 R for duration of 5-6 weeks. Concurrent or later chemotherapy increases the risk. It starts with  exudative phase, progress to organizing phase and to fibrotic phase.  It usually occurs 6 weeks up to 6 months after treatment. One diagnostic clue is its confinement to radiation portal. A straight line effect, which confines of the radiation port, is virtually diagnostic of radiation-induced lung injury. Exclusion of other possible causes of the findings, such as infection, thromboembolic disease, drug-induced pneumonitis etc. should be sought before final diagnosis. Further workup may require CT scan, ECHO and biopsy.

Steroids have been suggested as a treatment but may not be very helpful.