Other interstitial pneumonitis / fibrosis
Cryptogenic organizing pneumonia (Bronchiolitis obliterans-organizing pneumonia, BOOP)

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 7 October 2015, last major update September 2011

Copyright: (c) 2003-2015,, Inc.

PubMed Search: cryptogenic organizing pneumonia[title]
Cite this page: Cryptogenic organizing pneumonia (Bronchiolitis obliterans-organizing pneumonia, BOOP). website. Accessed November 18th, 2017.
Definition / general
  • Common response to infectious or inflammatory injury to lungs
  • Also associated with drugs, collagen vascular disease, and graft versus host disease in bone marrow transplant patients
  • Cause cannot be determined from biopsy - requires clinical history
  • Acute onset with cough, shortness of breath, fever and malaise
  • Excellent prognosis, but steroid resistance may lead to death
  • Steroids, however, some patients have self-limited disease
Microscopic (histologic) description
  • Patchy fibroblastic plugs in bronchioles and alveolar ducts (bronchiolitis obliterans) and alveoli (organizing pneumonia)
  • Plugs formed by spindled fibroblasts in pale-staining matrix with serpiginous or elongated shape
  • Also foamy macrophages, thickened alveolar septa and rare neutrophils
  • Low power: evenly spaced nodules or plugs of organizing connective tissue and inflammation that obliterates terminal airways
Microscopic (histologic) images

Courtesy of Dr. Semir Vranic