Bronchiolitis is a disease of the small airways, which are defined as airways less than 2 mm in diameter and without cartilage. The bronchioles are especially vulnerable to infectious or inhalational insults because of their narrow diameter.
A 60-year-old woman was seen in a pulmonary clinic because of increasing dyspnea. Chest imaging revealed bronchiectasis and mild, diffuse bronchial-wall thickening. A diagnostic procedure was performed. A new Case Record of the Massachusetts General Hospital summarizes.
Q: What are some of the general characteristics of bronchiolitis?
A: The primary symptoms of bronchiolitis are cough and dyspnea. Pulmonary-function testing reveals a nonreversible obstructive ventilatory defect and hyperinflation and often reveals diffusion impairment. Bronchiolitis may occur as a distinct clinical entity, such as acute bronchiolitis or obliterative bronchiolitis, or as part of an interstitial lung disease with bronchiolar involvement, such as respiratory bronchiolitis–associated interstitial lung disease. High-resolution computed tomography (CT) of the chest is the imaging study of choice, and characteristic findings include areas of gas trapping, bronchial-wall thickening, and centrilobular nodules.
Q: What is obliterative bronchiolitis?
A: Obliterative bronchiolitis, the histopathological equivalent of constrictive bronchiolitis, is a condition in which the airway lumen of the bronchioles becomes narrowed. Patients present with cough, dyspnea, and nonreversible airway obstruction. Obliterative bronchiolitis is progressive and can result in respiratory failure, because the bronchioles may ultimately become obliterated. As this disease advances, both bronchiectasis and diffusion abnormalities may develop. High-resolution CT reveals mosaic attenuation (i.e., areas of differing attenuation) and gas trapping.
Figure 1. Axial CT Scans of the Chest.
Figure 2. Lung-Biopsy Specimen.
Morning Report Questions
Q: What diseases or exposures are associated with obliterative bronchiolitis?
A: Obliterative bronchiolitis is rarely postinfectious. It has been described in conjunction with exposure to certain medications, including penicillamine and gold, and exposure to certain toxins, such as sulfur dioxide, sulfur mustard, nitrogen oxides, and the food flavoring diacetyl. The bronchiolitis obliterans syndrome refers to obliterative bronchiolitis that occurs during the post-transplantation period, specifically after allogeneic hematopoietic stem-cell transplantation and lung transplantation. Like many of the other types of bronchiolitis, obliterative bronchiolitis can be seen in patients with inflammatory bowel diseases and connective-tissue diseases; on rare occasions, it is idiopathic. Rheumatoid arthritis is the connective-tissue disease most frequently associated with bronchiolitis. It is important to note that, in some patients, the development of connective-tissue disease–associated lung disease can precede the development of the connective-tissue disease itself.
Q: What are some of the other types of bronchiolitis?
A: Acute bronchiolitis is infectious in origin and often caused by respiratory syncytial virus, although it can be seen with influenza, parainfluenza, adenovirus, and mycoplasma. Acute bronchiolitis primarily occurs in children but can occur in adults and is most often self-limiting. Diffuse panbronchiolitis primarily affects middle-aged Japanese men, causing a progressive disease that leads to bronchiectasis, to recurrent infections, and often sinusitis. Respiratory bronchiolitis is primarily seen in smokers and most often detected as an incidental finding on pathological examination of the lungs. Follicular bronchiolitis is also characterized by centrilobular nodules and ground-glass opacities on imaging studies of the chest and is associated with connective-tissue diseases (e.g., rheumatoid arthritis and Sjögren’s syndrome) and immunodeficiency syndromes (e.g., HIV and common variable immunodeficiency). Granulomatous bronchiolitis is a condition that can be seen with inflammatory bowel diseases with pulmonary involvement, interstitial lung diseases (e.g., hypersensitivity pneumonitis, sarcoidosis, and granulomatous–lymphocytic interstitial lung disease), and infectious causes (e.g., tuberculous and nontuberculous mycobacteria).
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