Organizing pneumonia (OP/BOOP)
(Fr: Pneumopathie organisée (BOOP). See also under If and XVc. A note of CAUTION: recent publications increasinly describe OP cases without lung pathology being documented. Basically, imaging is not reliable enough to confidently diagnose OP and such reports should be viewed with cauttion.
Organizing pneumonia is a clinical and a pathologic syndrome that may develop idiopathically or in association with an infection or hematologic, CTD or bowel disease unexposed to therapy drugs (PMID 16704928). Regardless of etiology, OP manifests with cough, fever, dyspnea and areas of parenchymal consolidation which may fluctuate or wander on serial imaging, multiple nodules, a mass or masses. Short of withdrawing the causal drug, serial relpases may occur even with continued corticosteroid therapy. Mild OP cases may not require steroid therapy. Suggestive OP features: 1) Migratory pulmonary opacities on sequential imaging, 2) Confirmatory pathology (not required in every case), 3) Lack of prominent BAL or tissue eosinophilia 4) Exposure to a compatible drug 5) Abatement of all signs and symptoms following drug discontinuance without corticosteroid therapy 6) Absence of relapse over at least one year follow-up. OP cases diagnosed on imaging only are considered low evidence (e.g. PMID 21761513). Only pathologically OP cases are included here and under OP in XV 'Pathology' . See also under 'Relapsing pneumonitis'.