Acute interstitial pneumonitis

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HR syndrome
Other names	Acute interstitial pneumonia or Hamman–Rich syndrome
Micrograph of diffuse alveolar damage, the histologic correlate of acute interstitial pneumonitis. H&E stain.
Specialty	Pulmonology

Acute interstitial pneumonitis (also known as acute interstitial pneumonia) is a rare, severe lung disease that usually affects otherwise healthy individuals. There is no known cause or cure.

Acute interstitial pneumonitis is often categorized as both an interstitial lung disease and a form of acute respiratory distress syndrome (ARDS). In uncommon instances, if ARDS appears acutely, in the absence of known triggers, and follows a rapidly progressing clinical course, the term "Acute interstitial pneumonia" is used.^[1] ARDS is distinguished from the chronic forms of interstitial pneumonia such as idiopathic pulmonary fibrosis.^[2]