Case Presentation: A 45-year-old female with PMH of hypertension presented with 3-days of worsening shortness of breath, general malaise and increasing home oxygen (O2) requirements. She was recently discharged from an outside hospital with home O2 and oral antibiotics for pneumonia.
The patient was admitted for acute hypoxemic respiratory failure presumed secondary to hospital-acquired pneumonia. She was tachycardic, tachypneic & saturating 87% on 4 liters O2 via nasal cannula. She appeared moderately distressed and was unable to speak in full sentences. Respiratory exam revealed bilateral rhonchi with multiple areas of egophony. Initial workup revealed leukocyte count of 14,000 and lactic acid of 2.2. Chest X-ray showed patchy nodular infiltrates bilaterally. Chest CT from an outside hospital showed bilateral nodular infiltrates with hilar adenopathy.

During hospital course, patient became increasingly hypoxic despite escalation in respiratory support, bronchodilator therapy and broad-spectrum antibiotics. Nasal swabs were negative for Influenza. Patient underwent bronchoscopy which showed very inflamed, friable mucosa that bled easily; Bronchoalveolar Lavage (BAL) cultures grew pan-sensitive Haemophilus parainfluenzae and Fusarium species. HIV, CMV and auto-immune work up was negative.

On the third day of hospitalization, the patient required mechanical ventilation. However, due to progressive worsening of respiratory status, a decision was made to initiate Extracorporeal Membrane Oxygenation (ECMO). At this point, lung biopsy was obtained which showed findings consistent with Acute Interstitial Pneumonia. Systemic steroid therapy was initiated, but on the fifth hospital day, patient progressed into multi-organ failure, severe metabolic acidosis and DIC. Patient’s immediate family and multidisciplinary care team made a shared decision that further aggressive care was futile.

Discussion: As seen in our patient, Acute Interstitial Pneumonia (AIP) affects healthy adults with a mean age of 50-55 and without prior history of lung disease or smoking. This disease rapidly progresses into a fatal form of acute lung injury that carries a mortality rate of more than 50%. The diagnosis entails a high level of clinical suspicion, carefully ruling out other etiologies like infections or autoimmune diseases. It is confirmed by biopsy showing diffuse alveolar damage. Our patient did grow pan-sensitive H. parainfluenzae and Fusarium in sputum, but this would not explain a fulminant disease in an otherwise healthy individual who received broad-spectrum antibiotics.

Conclusions: AIP, also known as Hamman-Rich Syndrome, is a rare and rapidly progressive form of acute lung injury of unknown etiology. This syndrome can also be referred to as Idiopathic Interstitial Pneumonia. We find that it is important to recognize and review AIP as a rare but probable cause of acute respiratory failure in patients suspected of having pneumonia that fails to respond to conventional treatment strategies. Mainstay of treatment for AIP consists of supportive care, often requiring mechanical ventilation due to respiratory failure. Glucocorticoids have not been proven to stop or limit the course of disease. For patients that do survive the acute phase, lung transplant may be considered.