Also known as Hamman-Rich syndrome. A rare form of idiopathic interstitial pneumonia characterized by acute onset and rapidly progressive course. Usually affects previously healthy individuals over the age of 40. Onset of symptoms is rapid, typically following a prodromal illness that lasts 1-2 weeks prior to presentation. At the time of presentation, patients have fever, cough, and progressive, severe shortness of breath, often leading to hypoxemia and mechanical ventilation. Physical exam features include fever, hypoxia, tachypnea, and diffuse crackles.
Progresses through three phases:
- An acute exudative phase characterized by temporally uniform lesions,
- An organized proliferative phase characterized by fibroblast proliferation and connective tissue formation, and finally
- A fibrotic phase characterized by collagen production, widening of alveolar septae, and organization of the alveolar exudate.
Prognosis is poor, with 50% of patients dying at the initial presentation and a majority of the surviving patients dying within 6 months of presentation. Those who do survive have variable residual lung function.