title: Bronchiolitis: adopting a unifying definition and a comprehensive etiological classification.
abstract: Bronchiolitis is an inflammatory and potentially fibrosing condition affecting mainly the intralobular conducting and transitional small airways. Secondary bronchiolitis participates in disease process of the airways and/or the surrounding lobular structures in the setting of several already defined clinical entities, mostly of known etiology, and occurs commonly. Primary or idiopathic bronchiolitis dominates and characterizes distinct clinical entities, all of unknown etiology, and occurs rarely. Secondary bronchiolitis regards infections, hypersensitivity disorders, the whole spectrum of smoking-related disorders, toxic fumes and gas inhalation, chronic aspiration, particle inhalation, drug-induced bronchiolar toxicities, sarcoidosis and neoplasms. Idiopathic or primary bronchiolitis defines clinicopathologic entities sufficiently different to be designated as separate disease entities and include cryptogenic constrictive bronchiolitis, diffuse panbronchiolitis, diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, neuroendocrine hyperplasia in infants, bronchiolitis obliterans syndrome in lung and allogeneic hematopoietic cell transplantation, connective tissue disorders, inflammatory bowel disease and bronchiolitis obliterans organizing pneumonia. Most of the above are pathological descriptions used as clinical diagnosis. Acute bronchiolitis, though potentially life threatening, usually regresses. Any etiology chronic bronchiolitis contributes to morbidity and/or mortality if it persists and/or progresses to diffuse airway narrowing and distortion or complete obliteration. Bronchiolitis in specific settings leads to bronchiolectasis, resulting in bronchiectasis.
authors.affiliation: 2nd Pulmonary Medicine Department, Attikon University Hospital, Athens Medical School, National and Kapodistrian University of Athens, Athens, Greece. papiris@otenet.gr
authors.forename: Spyros A
authors.initials: SA
authors.lastname: Papiris
authors.forename: Katerina
authors.initials: K
authors.lastname: Malagari
authors.forename: Effrosyni D
authors.initials: ED
authors.lastname: Manali
authors.forename: Likurgos
authors.initials: L
authors.lastname: Kolilekas
authors.forename: Christina
authors.initials: C
authors.lastname: Triantafillidou
authors.forename: Katerina
authors.initials: K
authors.lastname: Baou
authors.forename: Dimitra
authors.initials: D
authors.lastname: Rontogianni
authors.forename: Demosthenes
authors.initials: D
authors.lastname: Bouros
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kagouridis
mesh_terms: D056151:Airway Remodeling; D000818:Animals; D001706:Biopsy; D055745:Bronchioles / Q000473:pathology*; D001988:Bronchiolitis / Q000145:classification* / Q000175:diagnosis* / Q000209:etiology; D001995:Bronchography / Q000379:methods; D032921:Consensus; D018450:Disease Progression; D006801:Humans; D011237:Predictive Value of Tests; D011379:Prognosis; D012307:Risk Factors; D009626:Terminology as Topic; D014057:Tomography, X-Ray Computed