Acute interstitial pneumonitis must be differentiated from other diseases that present with respiratory failure and diffuse infiltrates on chest radiographs. Some of the differntials include ARDS, acute eosinophilic pneumonitis, Infections, hypersensitivity pneumonitis, connective tissue diseases, and drug-induced lung toxicity.

• Acute interstitial pneumonitis present with acute onset of respiratory symptoms resulting in severe hypoxia and respiratory failure.
• Any acute lung disease presenting with respiratory failure and show diffuse infiltrates on radiograph should be included in the differential diagnosis of acute interstitial pneumonitis.^[1]
  • Acute respiratory distress syndrome
  • Acute eosinophilic pneumonia
  • Acute hypersensitivity pneumonitis
  • Acute cryptogenic organizing pneumonia
  • Congestive heart failure
  • Acute exacerbation of Idiopathic pulmonary fibrosis
  • Diffuse alveolar hemorrhage:
    • Vasculitis-induced:
      • Antiphospholipid antibody syndrome
      • Behcet’s syndrome
      • Goodpasture’s syndrome
      • Microscopic polyangiitis
      • Wegener’s granulomatosis
    • Bland hemorrhage
      • coagulopathy
      • idiopathic pulmonary hemosiderosis
      • Mitral stenosis
  • Drug toxicity
  • Infection
  • Radiation therapy
  • Noninfectious pulmonary complications of hematopoietic stem-cell or solid-organ transplantation
  • Inhalation/toxic exposure