title: Micronodular pattern of organizing pneumonia: Case report and systematic literature review.
abstract: BACKGROUND
  Organizing pneumonia (OP) is a clinicopathological entity characterized by granulation tissue plugs in the lumen of small airways, alveolar ducts, and alveoli. OP can be cryptogenic (primary) (COP) or secondary to various lung injuries.
  
  
  METHODS
  We report the case of a 38-year-old male smoker with COP presenting in the form of diffuse micronodules on computed tomography (CT) scan and describe the clinical, radiological, and functional characteristics of micronodular pattern of organizing pneumonia (MNOP) based on a review of the literature including 14 cases.Patients were younger (36.3 ± 15.5 years) than those with the classical form of OP. The clinical presentation was subacute in all cases with a mean duration of symptoms before admission of 14.5 ± 13.2 days. The radiological pattern was characterized by centrilobular nodules and "bud-in-tree" sign in 86.7% of patients. The diagnosis was based on histological examination of transbronchial (28.6%) or surgical biopsies (71.4%).
  
  
  METHODS
  An associated condition was identified in 65% of cases and included illicit substance abuse (44.5%), myeloproliferative disease (33.5%), and infections (22%).
  
  
  RESULTS
  Steroid therapy was effective in all patients with improvement of symptoms and documented radiologic resolution. No relapse was recorded.
  
  
  CONCLUSIONS
  MNOP should be recognized and distinguished from other diagnoses, mainly infectious bronchiolitis and disseminated tumor, as it requires early specific steroid therapy.
authors.affiliation: Department of Respiratory Diseases, Reims University Hospital EA 4683 Medical and Pharmacological University of Reims Radiology Department INSERM UMRS 903 Department of Cardio-Thoracic Surgery, Reims University Hospital, Reims, France.
authors.forename: François
authors.initials: F
authors.lastname: Lebargy
authors.forename: Davy
authors.initials: D
authors.lastname: Picard
authors.forename: Jean
authors.initials: J
authors.lastname: Hagenburg
authors.forename: Olivier
authors.initials: O
authors.lastname: Toubas
authors.forename: Jeanne-Marie
authors.initials: JM
authors.lastname: Perotin
authors.forename: Sebastian
authors.initials: S
authors.lastname: Sandu
authors.forename: Gaëtan
authors.initials: G
authors.lastname: Deslee
authors.forename: Sandra
authors.initials: S
authors.lastname: Dury
mesh_terms: D000328:Adult; D018549:Cryptogenic Organizing Pneumonia / Q000175:diagnosis / Q000473:pathology*; D006801:Humans; D008168:Lung / Q000473:pathology*; D008297:Male