[Extrinsic allergic alveolitis].

Extrinsic allergic alveolitis (EAA) or hypersensitivity pneumonitis is an interstitial lung disease associated with repeated exposure to a wide range of inhaled organic dusts and related occupational allergens, especially bird and fungal proteins. We focus on the diagnostic and prognostic findings related to the use of BAL in the management of EAA patients. The presentation of EAA varies from patient to patient and is mainly related to the frequency and intensity of exposure to the causative antigens. In addition, the different amounts of inhaled antigens and the timing of observation might be crucial. For this reason we will refer to the acute, subacute or chronic phases of the clinical picture rather than to the active and inactive forms of the disease.