Abstract
Cryptogenic organizing pneumonia (COP), formerly called bronchiolitis obliterans organizing
pneumonia (BOOP), was first described in the 1980s and is classified as a rare idiopathic
interstitial pneumonia (IIP). COP classically presents in a subacute fashion following
a flu-like illness with fever, non-productive cough, and fatigue. Imaging often reveals
diffuse, bilateral, peribronchovascular and peripheral, consolidative and ground-glass
opacities although various imaging subtypes also exist. Physical examination may be
normal or reveal inspiratory crackles. Hypoxemia, when present, is commonly identified
with exertion but can also occur at rest. Diagnostic evaluation relies on excluding
secondary causes of organizing pneumonia and includes a thorough history including
medications, exposures, and signs or symptoms of underlying rheumatologic disease.
Invasive diagnostic testing including tissue sampling allows for histopathologic confirmation
of COP while excluding secondary causes including infection and malignancy. Although
video-assisted thoracoscopic surgery (VATS) lung biopsy is often the preferred method
of obtaining sufficient tissue, less invasive means may be employed based on patient-specific
factors. A defining feature of COP is steroid-responsiveness, and most experts recommend
prolonged corticosteroid courses (6–12 months). Response to corticosteroids and prognosis
are typically excellent. Relapse rates range from 25 to 50% and occur most often during
steroid taper or complete withdrawal necessitating additional therapy. Steroid-sparing
immunosuppression may be used in select circumstances. Further study is needed to
define optimal corticosteroid dose and duration.
Keywords cryptogenic organizing pneumonia (COP) - organizing pneumonia (OP) - idiopathic interstitial
pneumonia (IIP) - bronchiolitis obliterans organizing pneumonia (BOOP) - interstitial
lung disease (ILD)
