Acute interstitial pneumonia

The term "acute interstitial pneumonia" (AIP) describes an idiopathic clini copathological condition, characterized clinically by an interstitial lung disease causing rapid onset of respiratory failure, which is distinguishabl e from the other more chronic forms of interstitial pneumonia, It is synony mous with Hamman-Rich syndrome, occurring in patients without pre-existing lung disease. The histopathological findings are those of diffuse alveolar damage. AIP ra diologically and physiologically resembles acute respiratory distress syndr ome (ARDS) and is considered to represent the small subset of patients with idiopathic ARDS. It is frequently confused with other clinical entities ch aracterized by rapidly progressive interstitial pneumonia, especially secon dary acute interstitial pneumonia, acute exacerbations and accelerated form s of cryptogenic fibrosing alveolitis. Furthermore, many authors use the ab ove terms, both erroneously and interchangeably. It has a grave prognosis w ith >70% mortality in 3 months, despite mechanical ventilation. This review aims to clarify the relative clinical and pathological issues a nd terminology.