Small airways diseases, excluding asthma and COPD: an overview

Abstract

This review is the summary of a workshop on small airways disease, which took place in Porquerolles, France in November 2011. The purpose of this workshop was to review the evidence on small airways (bronchiolar) involvement under various pathophysiological circumstances, excluding asthma and chronic obstructive pulmonary disease. Histopathological patterns associated with small airways disease were reviewed, including cellular and obliterative bronchiolitis. Many pathophysiological conditions have been associated with small airways disease including airway infections, connective tissue diseases and inflammatory bowel diseases, bone marrow and lung transplantation, common variable immunodeficiency disorders, diffuse panbronchiolitis, and diseases related to environmental exposures to pollutants, allergens and drugs. Pathogenesis, clinical presentation, a computed tomography scan and pulmonary function test findings are reviewed, and therapeutic options are described with the objective of providing an integrative approach to these disorders.

Keywords: Airway pathology; connective tissue disease; constrictive bronchiolitis; drug-induced lung disease; follicular bronchiolitis; immune deficiency.

Figure 1.

Representative photomicrographs of individual bronchiolar lesions observed in surgical lung biopsy in patients with small airways disease. a) Cellular bronchiolitis: a narrowed and contracted airway is infiltrated by numerous inflammatory cells without a specific pattern. b) Granulomatous bronchiolitis: the small airway is surrounded by an inflammatory infiltrate with a sarcoid granuloma (arrowheads), which increases the volume of the airway wall resulting in lumen narrowing. c) Follicular bronchiolitis: the small airway is surrounded by a large lymphoid follicule (arrowheads), which increases the volume of the airway wall resulting in lumen narrowing. d) Bronchiolitis obliterans is characterised by lumen obstruction with a fibro-inflammatory polyp. e) Obliterative (constrictive) bronchiolitis: the airways lumen is narrowed by subepithelial fibrosis. Although inflammatory cells and mucous exudates are present within the lumen, no fibro-inflammatory polyp is found. f) Mucous plugging: the airway lumen is obstructed by mucus exudates.

Figure 2.

Representative images of computed tomography (CT) scans in patients with small airways disease. a) An inspiratory CT scan in a patient with hypersensitivity pneumonitis showing mosaic pattern of attenuation. b) Expiratory CT scan in the same patient showing air trapping that is characteristic of small airways disease. c) Ill-defined centrilobular nodules in a patient with farmer's lung (personal communication; J.C. Dalphin). d) Localised micronodules branching with bronchovascular structures (tree-in-bud pattern) related to tuberculosis in a patient with rheumatoid arthritis receiving treatment with anti-tumour necrosis factor-α. Reproduced from [21] with permission from the publisher.