title: Biopsy-proven pulmonary capillaritis: A retrospective study of aetiologies including an in-depth look at isolated pulmonary capillaritis.
abstract: OBJECTIVE
  Pulmonary capillaritis is generally secondary to a systemic autoimmune process. Little is known regarding other causes of pulmonary capillaritis, particularly isolated pulmonary capillaritis (IPC). IPC is defined as pulmonary capillaritis in the absence of evidence of a systemic disease. We aim to describe the aetiology of biopsy-proven pulmonary capillaritis to add to the existing knowledge on aetiologies of pulmonary capillaritis and provide a more detailed description of IPC cases.
  
  
  METHODS
  A retrospective cohort of biopsy-proven pulmonary capillaritis was conducted at the Mayo Clinic, Rochester over a 17-year period. Histologic slides were re-reviewed by a lung pathologist. Medical records were reviewed to identify a possible aetiology of the pulmonary capillaritis. A subset analysis of patients identified with IPC was then performed.
  
  
  RESULTS
  Thirty-six cases of biopsy-proven pulmonary capillaritis were identified. The majority of cases were secondary to a systemic autoimmune disease, most commonly granulomatosis with polyangiitis. There were four cases of IPC in this cohort. Median follow-up was 116.5 months with no evidence of systemic disease development. No risk factors for IPC were identified. All patients presented sub-acutely with haemoptysis and diffuse alveolar haemorrhage with a delay in diagnosis. After initiation of immunosuppression, most patients obtained remission with a benign clinical course.
  
  
  CONCLUSIONS
  Pulmonary capillaritis is most commonly secondary to systemic autoimmune disorders, predominantly ANCA-associated vasculitis. IPC is a rare form of pulmonary capillaritis with very few cases described in the literature, the availability of effective treatment makes this rare disease important to recognize.
authors.affiliation: Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Gwen
authors.initials: G
authors.lastname: Thompson
authors.affiliation: Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Klecka
authors.affiliation: Division of Anatomic Pathology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Anja C
authors.initials: AC
authors.lastname: Roden
authors.affiliation: Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA.|Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Specks
authors.affiliation: Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA.|Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Cartin-Ceba
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000150:complications; D001706:Biopsy; D002196:Capillaries / Q000473:pathology*; D005260:Female; D006469:Hemoptysis / Q000209:etiology; D006801:Humans; D008168:Lung / Q000098:blood supply*; D008171:Lung Diseases / Q000175:diagnosis / Q000209:etiology* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014657:Vasculitis / Q000175:diagnosis / Q000209:etiology* / Q000473:pathology*; D055815:Young Adult
keywords: autoimmune disease; immunosuppression; lung disease; prognosis; vasculitis