[Diagnostic approach to new or unrecognized risks in hypersensitivity pneumopathies].

Hypersensitivity pneumonitis is one model of environmental pulmonary disease. If the clinical and radiological pictures are now well established the risk of allergic disorders in the community can only be appreciated by large epidemiological enquiries which ought to be carried out with the utmost vigor, yet may be deceptive. As regards diagnosis, one should take note on the one hand of: --respiratory function tests showing the involvement of the alveoli and the interstitium in the pathological process but also that of the peripheral bronchioles, that is the distal lung as a whole. --On the other hand systemic immunological studies (search for precipitating antibodies to allergens, always considered to be a diagnostic test of major value) may nonetheless be reinforced by cell counts lymphocytes) or skin tests and even provocation tests. --The study of bronchoalveolar lavage yields very important information: An increase in the number of cells, notably " T " lymphocytes, biochemical disturbances characterized by an increase in protein and lipid levels with qualitative changes in the phospholipids: a fall in the lecithin and a rise of the other fractions which lead to an increase in the microviscosity of alveolar liquid. Finally an aetiological study is required to identify the allergen in the ambient atmosphere of the patient or worker and if possible, an experimental study trying to reproduce the pathological lesions and the immunological disturbances. Finally the treatment should consist of excluding the offending agent. Steroid therapy is justified in acute situations with disturbed function, but this does not prevent a final outcome of irreversible fibrosis.