P ulmonary
Aliya N. Husain, M.D.
XIII. Iatrogenic Diseases
A. Drug reactions: Three broad groups of drug reactions can be recognized in the lung.

  1. Toxic or dose related: There is diffuse alveolar damage in the early or organizing phase. Later on interstitial scarring and honeycombing may be seen.
  2. 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.
  3. 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.
    1. Busulphan: Bizarre hyperchromatic Type II pneumocytes.
    2. Methotrexate: Small granulomas are seen in one-third to one-half of all cases of methotrexate pneumonitis.
    3. Amiodarone toxicity: Histiocytes within airspaces contain cytoplasmic vacuoles which are characteristic but not diagnostic.
B. Radiation pneumonitis: Early damage has the appearance of DAD. Chronic pneumonitis resembles UIP, with vascular intimal thickening with atypical fibroblasts, foamy cells, and bizarre endothelial cells and atypical Type II pneumocyte hyperplasia. These changes are characteristic but nonspecific and can also be seen after infections.