[Acute interstitial pneumonia: diagnostic approach and management].

Acute interstitial pneumonia (AIP) encompasses a spectrum of pulmonary disorders characterized by involvement of the lung interstitium and distal airways (bronchioles and alveoli). The onset of respiratory symptoms is acute, most often within two weeks. Most AIP take place de novo, but sometimes represent an acute exacerbation of chronic lung disease. The clinical presentation of AIP comprises rapidly progressive dyspnoea, associated sometimes with cough, fever, myalgia and asthenia. Chest radiography shows diffuse pulmonary opacities. The associated hypoxemia may be severe enough to cause acute respiratory failure. Underlying aetiologies are numerous and variable, particularly in relation to the underlying immune status of the host. Various histopathological entities may be responsible for AIP although diffuse alveolar damage is the predominant pattern. The diagnostic approach to a patient presenting with AIP is to try to determine the most likely underlying histopathological pattern and to search for a precise aetiology. It relies mainly on a meticulous clinical evaluation and accurate biological investigation, essentially guided by the results of bronchoalveolar lavage performed in an area identified by abnormalities on high resolution computed tomography of the lungs. Initial therapeutic management includes symptomatic measures, broad-spectrum antibiotic treatment adapted to the clinical context, frequently combined with systemic corticosteroid therapy.