IDIOPATHIC BRONCHIOLITIS OBLITERANS ORGANIZING PNEUMONIA CRYPTOGENIC ORGANIZING PNEUMONIA WITH UNFAVORABLE OUTCOME - PATHOLOGICAL PREDICTORS

Idiopathic bronchiolitis obliterans organizing pneumonia (BOOP) and cr yptogenic organizing pneumonia (COP) are synonyms for an inflammatory interstitial process characterized by young fibromyxoid connective tis sue within airways and air spaces, This clinicopathologic condition is associated with an excellent response to steroidal therapy in more th an 80% of patients, In this study, we examined matched groups of 10 pa tients with steroid-responsive idiopathic BOOP/COP and 9 patients with idiopathic BOOP/COP two fared poorly despite therapy, No significant differences in demographics, symptoms, or radiographic appearances wer e noted between the two cohorts, Histologic examination revealed that the cases with progressive, idiopathic BOOP/COP were accompanied by sc arring and remodeling of the background lung parenchyma in 89% of case s, in contrast to 10% of those with a good prognosis. This finding pro vided a potential morphologic marker of outcome for therapy in idiopat hic BOOP/COP, Steroid-nonresponsive cases of BOOP/COP may have a prope nsity to cause irreversible injury to the lung, a feature not seen in cases with a good outcome, Another explanation may be that such cases represent a BOOP/COP-like reaction pattern in patients with an associa ted fibrosing interstitial pneumonia, especially usual interstitial pn eumonia, The differential diagnosis of BOOP/COP with organizing diffus e alveolar damage, eosinophilic pneumonia, and other chronic interstit ial pneumonias is discussed.