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"Bronchiolitis obliterans characteristically presents with the insidious onset of a nonproductive cough and dyspnea 2 to 8 weeks after an acute respiratory illness or toxic exposure." [Murray, p. 1297] "The spectrum of occupational COPD also encompasses exposure to toxic agents which cause irreversible inflammatory disease in the terminal bronchioles, respiratory bronchioles, and alveolar ducts. The unique histopathology features of bronchiolitis (B) and bronchiolitis obliterans (BO) clearly distinguish these airway diseases from other COPD entities. . . . Acute injury by toxic gases is a common cause of BO and has been reported after inhalation of high concentrations of nitrogen dioxide, sulfur dioxide, ammonia, hydrogen fluoride, phosgene, hydrogen bromide, and hydrogen chloride." Other possible causes of BO include methyl isocyanate and diacetyl. [Asthma in the Workplace, p. 697] BO has also been reported after hydrogen sulfide poisoning and in nylon-flock workers, textile workers (polyamide-amine dyes), and workers in microwave popcorn plants (diacetyl). [Ladou, p. 330] Chest x-ray findings are normal or show hyperinflation. Spirometry usually shows a mixed obstructive/restrictive defect. [Hendrick, p. 99] "The key HRCT findings described in constrictive obliterative bronchiolitis are; areas of parenchymal decreased attenuation giving rise to the so-called 'mosaic attenuation pattern', pulmonary vascular attenuation, bronchial wall thickening and dilatation and air trapping on expiratory CT." [Hendrick p. 497] |
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