|A. Drug reactions: || Three broad groups of drug reactions can be recognized in the lung.|
- Toxic or dose related: There is diffuse alveolar damage in the early or organizing phase. Later on interstitial scarring and honeycombing may be seen.
- Idiosyncratic or allergic reactions: These include bronchiolitis obliterans, BOOP, nonspecific interstitial inflammation, granulamatous interstitial pneumonia, eosinphilic pneumonia, UIP, DIP, LIP vasculitis and mixtures of above.
- Miscellaneous reactions, a few of which have specific features: These include pulmonary edema, alveolar hemorrhage, histiocytic infiltrates and phospholipidosis (amiodarone), metastatic calcification, asthma, foreign body giant cell reaction (IV talcosis), pulmonary hypertension, pleuritis and veno-occlusive disease.
- Busulphan: Bizarre hyperchromatic Type II pneumocytes.
- Methotrexate: Small granulomas are seen in one-third to one-half of all cases of methotrexate pneumonitis.
- Amiodarone toxicity: Histiocytes within airspaces contain cytoplasmic vacuoles which are characteristic but not diagnostic.