Skip to Main Content

++

HYPERSENSITIVITY PNEUMONITIS

++

INTRODUCTION AND DEFINITION

++

Hypersensitivity pneumonitis (HP), also referred to as extrinsic allergic alveolitis, is a pulmonary disease that occurs due to inhalational exposure to a variety of antigens leading to an inflammatory response of the alveoli and small airways. Systemic manifestations such as fever and fatigue can accompany respiratory symptoms. Although sensitization to an inhaled antigen as manifested by specific circulating IgG antibodies is necessary for the development of HP, sensitization alone is not sufficient as a defining characteristic, because many sensitized individuals do not develop HP. The incidence and prevalence of HP are variable, depending on geography, occupation, avocation, and environment of the cohort being studied. As yet unexplained is the decreased risk of developing HP in smokers.

++

OFFENDING ANTIGENS

++

HP can be caused by any of a large list of potential offending inhaled antigens (Table 310-1). The various antigens and environmental conditions described to be associated with HP give rise to an expansive list of monikers given to specific forms of HP. Antigens derived from fungal, bacterial, mycobacterial, bird-derived, and chemical sources have all been implicated in causing HP.

++
Table Graphic Jump Location
TABLE 310-1Examples of Hypersensitivity Pneumonitis

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.