Occupational Hypersensitivity Pneumonitis

Abstract

Hypersensitivity pneumonitis (HP), or extrinsic allergic alveolitis, is a relatively rare condition with a variable natural history (acute, subacute, or chronic) and fairly nonspecific features. Patients present with pulmonary symptoms with or without constitutional disturbance. HP can be caused by >300 different agents, which broadly comprise microbial agents (bacteria, fungus), animal antigens, and chemicals, and exposure to these agents may occur in occupational settings—the focus of this article—or elsewhere. HP, particularly due to occupational exposures, is underdiagnosed due to a lack of awareness of the condition and difficulties in identifying and confirming the diagnosis. Bird fancier’s lung and farmer’s lung have historically been the most common causes of HP. More recently, metalworking fluids used in engineering have emerged as an increasingly common etiological agent for occupational HP and several outbreaks have been reported. Making a diagnosis of occupational HP is crucial both for the individual, so as to remove them from exposure and maximize the chance of a full recovery, and for the employer, so that they can identify other cases and put into place strategies to prevent further cases. There is no single gold standard test used to confirm HP, and a combination of a careful occupational exposure history, clinical history, radiology, and immunology findings can help ascertain a diagnosis. Certain key questions can be useful in eliciting a work-related pattern to symptoms.