Difference Between Pneumonia and Pneumonitis

Published: April 7, 2016
Last reviewed: March 20, 2018

Pneumonia and Pneumonitis Definition

Pneumonitis means lung inflammation.

Word origin: from the Greek pneúmon = lung, and the Latin -itis, which denotes inflammation

The terms pneumonia and pneumonitis are not clearly defined, but the current usage among doctors is as following:

  • Pneumonia is lung inflammation from infection.
  • Pneumonitis is lung inflammation from causes other than infection.

In the medical literature, the two terms are not always used strictly according to the above rule. The examples of lung conditions called pneumonia not caused by infections are lipoid pneumonia and eosinophilic pneumonia. An example of a condition called pneumonitis but caused by microbes is viral pneumonitis, caused by H1N1 Influenza virus or Varicella-zoster virus. Apart from that, a group of lung diseases that affect the spaces between the alveoli (interstitial space) can be called either interstitial pneumonia or interstitial pneumonitis regardless of the cause.

Both pneumonia and pneumonitis can cause either inflammation of the lung air sacs (alveoli) with fluid accumulation in them or only spaces between them (interstitium), so the term pneumonia or pneumonitis alone tells nothing about the type of the lung tissue damage (pathology).

Pneumonitis usually has a sudden onset, the cough is usually dry and there is no or only low-grade fever. Pneumonia can develop suddenly or gradually and the affected person can cough up mucus or not and can have a fever or not. Both conditions can be life-threatening if not treated properly.

Pneumonia vs Pneumonitis



 Causes  Bacteria, viruses, fungi
  • Aspiration of gastric acid or vomit
  • Inhalation of toxic gases, dust or molds
  • Adverse reaction to drugs
  • Complication of autoimmune diseases, such as systemic lupus erythematosus (SLE)
 Affected lung part  Alveoli or interstitium  Alveoli or interstitium
 Is it  contagious?  Yes  No
 Who can get it?  Anyone, but especially infants, elderly and those with weak immune  system  Persons who vomit while drunk, farmers sensitive to dust and molds, workers in chemical or textile industry, individuals with low immunity or autoimmune diseases
 Symptoms  Coughing up sputum, shortness of breath,  fever (or no sputum or fever)  Shortness of breath, dry cough (occasionally low-  grade fever)
 Symptoms  duration  1 week to few months  Few hours to days (months or even lifelong if it becomes chronic)
 Diagnosis  X-ray, blood and sputum culture  CT, lung biopsy
 Treatment  Antibiotics, antivirals, antifungals, oxygen  Steroids, oxygen
 Prevention  Avoid contact with infected persons  Avoid dust, molds or wear a protective mask

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