Diagnosis

Acute interstitial pneumonia

Etiology

Cause [4hm]

Acute interstitial pneumonia has no known etiology.

Pathophysiology [4hm]

1. Unknown insult to the alveolar epithelium

2. Activation of the inflammatory cascade --> symmetric diffuse alveolar damage

3. Fibroblastic activity in the late stage --> pulmonary fibrosis

Epidemiology

Incidence per 100.000 [d5p][eip]

Approach

• Blood tests: blood culture, autoimmune screening (rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, Sjogren syndrome)

• Arterial blood gas: PaO2/FiO2-ratio

• Sputum culture

• Spirometry

• Chest x-ray

• CT thorax: diffuse ground glass and alveolar consolidation opacities, honeycomb fibrosis i later phase

• Echocardiography

• Bronchoscopy with bronchoalveolar lavage: bronchiectasia

• Biopsy

Major Criteria (Must Have All Four): [eip]

1. Exclusion of other known causes (drug toxicities, environmental exposures, and connective tissue diseases)

2. Restrictive pulmonary failure (reduced vital capacity, increased FEV1/FVC ratio) and impaired gas exchange

3. Bibasilar reticular abnormalities with minimal ground-glass opacities on HRCT scans

4. Transbronchial lung biopsy or BAL showing no features to support an alternative diagnosis 

Minor Criteria (Must Have Three of Four) 

1. Age > 50 yr

2. Insidious onset of otherwise unexplained dyspnea on exertion

3. Duration of illness > 3 mo 

4. Bibasilar, inspiratory crackles

Treatment

1. There is no proven treatment. Management is largely based on supportive care [rds][4hm]

   • Mechanical ventilation (low tidal volume ventilation)

   • Corticosteroid therapy: uncertain efficacy

   • Broad-spectrum antibiotics until infectious etiology is excluded

   • Extracorporeal membrane oxygenation (ECMO)

2. Lung transplantation should be considered for appropriate candidates after failing conventional therapy [4hm]

Differential diagnoses

Acute pancreatitis, Acute respiratory distress syndrome, COPD, Drug side effects, Eosinophilic pneumonia, Heart failure, Inhalation injury, Interstitial lung disease, Pneumonia, Pneumonitis, Pulmonary fibrosis