A new pattern of lung injury that began after a drug — organising pneumonia, NSIP, HP-like, diffuse alveolar damage — in a patient on amiodarone, methotrexate, bleomycin, nitrofurantoin or immune checkpoint inhibitors; the report names the pattern and the time course.
Orient first
- Patterns are not drug-specific; the temporal relation to the drug is the clue (pneumotox.com lists associations).
- Checkpoint-inhibitor pneumonitis is graded clinically (CTCAE) — radiology shows the pattern and extent.
- Amiodarone: high-attenuation liver and lung consolidation.
Acquire the study
- High-resolution CT chest, thin sections; compare with the pre-treatment CT.
The manoeuvre
- Compare with the baseline CT: new opacities since the drug started.
- Lung window: name the pattern — organising pneumonia, NSIP, HP-like, DAD, eosinophilic.
- Extent: percentage of lung involved, lobar distribution.
- Soft-tissue window: high attenuation of the liver and consolidation (amiodarone).
- Exclude infection and tumour progression (lymphangitic spread, new nodules).
What confirms it
- A new pattern after exposure, other causes excluded, with improvement on withdrawal.
What licenses you to exclude it
- Opacities predating the drug, or proven infection, make drug toxicity less likely.
The classic misread
- Calling pneumonitis progression of cancer in a patient on immunotherapy.