Acute interstitial pneumonitis
Acute interstitial pneumonitis (AIP) is a rapidly progressive non infectious interstitial lung disease of unknown aetiology. It is considered the only acute process of the idiopathic intersitial pneumonias.
It tends to occur in those without pre-existing lung disease. Typically affects middle age adults (mean ~ 50 years 5)
Clinical features are often wide. Patients often have a history of an antecedent prior illness such as a viral upper respiratory infection. Common initial symptoms include myalgias, arthralgias, pyrexia, chills, and malaise. Severe exertional dyspnea develops over a matter of days.
Characterised histologically by diffuse alveolar damage (DAD) 2. The alveolar damage comprises of three phases, an acute exudative phase, a subsequent organising phase and a final fibrotic phase. Histological features are very similar with that of the adult respiratory distress syndrome (ARDS).
The correct clinical context is vital for image interpretation.
Non specific and often shows bilateral patchy airspace opacification
During intialy stages can have similar features to adult respiratory distress syndrome (ARDS).
- areas with ground-glass attenuation : generally tends to be bilateral and symmetrical 10
- traction bronchiectasis : can be seen in ~ 80 % of cases during the course of the disease 4 and correlates with disease duration 2
- lung parechymal architectural distortion
- air space consolidation : may have a slight predilection towards the dependent portions 5
Treatment and prognosis
The condition usually progresses to respiratory failure that requires mechanical ventilation and corticosteroid therapy. Even despite mechanical ventilation, it often tends to carry a grave prognosis with >70% mortality at ~ 3 months 1,
- clinical features first described by L Hamman and A Rich in 1935 8
- pathological processes first described by A L Katzenstein et.al in 1986 3.
Considerations in early stages include
- adult respiratory distress syndrome (ARDS) : can have other ogran involvement 9
- infectious multifocal pneumonia
For the more general differential, consider
- 1. Bouros D, Nicholson AC, Polychronopoulos V et-al. Acute interstitial pneumonia. Eur. Respir. J. 2000;15 (2): 412-8. Eur. Respir. J. (link) - Pubmed citation
- 2. Johkoh T, Müller NL, Taniguchi H et-al. Acute interstitial pneumonia: thin-section CT findings in 36 patients. Radiology. 1999;211 (3): 859-63. Radiology (full text) - Pubmed citation
- 3. Katzenstein AL, Myers JL, Mazur MT. Acute interstitial pneumonia. A clinicopathologic, ultrastructural, and cell kinetic study. Am. J. Surg. Pathol. 1986;10 (4): 256-67. - Pubmed citation
- 4. Tomiyama N, Müller NL, Johkoh T et-al. Acute parenchymal lung disease in immunocompetent patients: diagnostic accuracy of high-resolution CT. AJR Am J Roentgenol. 2000;174 (6): 1745-50. AJR Am J Roentgenol (full text) - Pubmed citation
- 5. Wittram C, Mark EJ, Mcloud TC. CT-histologic correlation of the ATS/ERS 2002 classification of idiopathic interstitial pneumonias. Radiographics. 23 (5): 1057-71. doi:10.1148/rg.235035702 - Pubmed citation
- 6. Silva CI, Müller NL. Idiopathic interstitial pneumonias. J Thorac Imaging. 2009;24 (4): 260-73. doi:10.1097/RTI.0b013e3181c1a9eb - Pubmed citation
- 7. Vourlekis JS, Brown KK, Cool CD et-al. Acute interstitial pneumonitis. Case series and review of the literature. Medicine (Baltimore). 2000;79 (6): 369-78. Medicine (Baltimore) (link) - Pubmed citation
- 8 Hamman, L, Rich, A Fulminating diffuse interstitial fibrosis of the lungs. Trans Am Clin Clinatol Assoc 1935;51,154-163
- 9. Quefatieh A, Stone CH, Digiovine B et-al. Low hospital mortality in patients with acute interstitial pneumonia. Chest. 2003;124 (2): 554-9. doi:10.1378/chest.124.2.554 - Pubmed citation
- 10.Primack SL, Hartman TE, Ikezoe J et-al. Acute interstitial pneumonia: radiographic and CT findings in nine patients. Radiology. 1993;188 (3): 817-20. Radiology (abstract) - Pubmed citation
- 11. Mueller-mang C, Grosse C, Schmid K et-al. What every radiologist should know about idiopathic interstitial pneumonias. Radiographics. 27 (3): 595-615. doi:10.1148/rg.273065130 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Acute interstitial pneumonia||✓|
|Acute interstitial pneumonitis (AIP)||✗|