Extrinsic allergic alveolitis

Abstract

Extrinsic allergic alveolitis (EAA) belongs to the family of interstitial lung diseases. It results from repeated inhalation of causative antigens in susceptible individuals. The two most adequately studied and best known forms of EAA are farmer's lung and pigeon breeder's disease. The clinical presentation of the disease has been defined as acute, subacute and chronic. For the acute form of the disease, which occurs several hours after the antigen challenge, an immune-complex-mediated tissue injury is typical. However, a T-cell mediated immune inflammatory response prevails in advanced stages of the disease. No commonly accepted diagnostic criteria have yet been published. The most important step is to consider EAA in the differential diagnosis of any interstitial lung disease and to review the patient's occupational and environmental history. There are no pathognomic clinical, radiographic, laboratory or histologic abnormalities for EAA. Avoidance of sensitising antigen is the key element of the treatment regime. Corticosteroids are recommended in acute, severe and progressive disease. Acute pigeon breeder's disease appears to have favorable prognosis. Patients with progressive and irreversible pulmonary damage have a fairly high risk of death.