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Pneumonia is an inflammatory condition of the lung.[1] It is often characterized as including inflammation of the parenchyma of the lung (that is, the alveoli) and abnormal alveolar filling with fluid (consolidation and exudation).[2]

The alveoli are microscopic air filled sacs in the lungs responsible for gas exchange. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as unknown when infectious causes have been excluded.

Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum. Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics.

Pneumonia is common, occurring in all age groups, and is a leading cause of death among the young, the old, and the chronically ill.[3] Vaccines to prevent certain types of pneumonia are available. The prognosis depends on the type of pneumonia, the treatment, any complications, and the person’s underlying health.



Pneumonia can be caused by microorganisms, irritants and unknown causes. When pneumonias are grouped this way, infectious causes are the most common type. The symptoms of infectious pneumonia are caused by the invasion of the lungs by microorganisms and by the immune system‘s response to the infection. Although more than one hundred strains of microorganism can cause pneumonia, only a few are responsible for most cases. The most common causes of pneumonia are viruses and bacteria. Less common causes of infectious pneumonia are fungi and parasites.

Signs and symptoms


Pneumonia fills the lung’s alveoli with fluid, keeping oxygen from reaching the bloodstream. The alveolus on the left is normal, while the alveolus on the right is full of fluid from pneumonia.



Main symptoms of infectious pneumonia, click play to hear the sounds of an actual Pneumonia Patient.

Crackles heard in the lungs of a person with pneumonia using a stethoscope.

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People with infectious pneumonia often have a cough producing greenish or yellow sputum, or phlegm and a high fever that may be accompanied by shaking chills. Shortness of breath is also common, as is pleuritic chest pain, a sharp or stabbing pain, either experienced during deep breaths or coughs or worsened by them. People with pneumonia may cough up blood, experience headaches, or develop sweaty and clammy skin. Other possible symptoms are loss of appetite, fatigue, blueness of the skin, nausea, vomiting, mood swings, and joint pains or muscle aches. Less common forms of pneumonia can cause other symptoms; for instance, pneumonia caused by Legionella may cause abdominal pain and diarrhea, while pneumonia caused by tuberculosis or Pneumocystis may cause only weight loss and night sweats. In elderly people, manifestations of pneumonia are seldom typical. They may develop a new or worsening confusion (delirium) or may experience unsteadiness, leading to falls. Infants with pneumonia may have many of the symptoms above, but in many cases they are simply sleepy or have a decreased appetite.[9]



See also


  1. ^ pneumonia at eMedicine Dictionary
  2. ^ pneumonia at Dorland’s Medical Dictionary
  3. ^ “Causes of death in neonates and children under five in the world (2004)”. World Health Organization.. 2008.
  4. ^ a b c d Table 13-7 in: Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson (2007). Robbins Basic Pathology (8th ed.). Philadelphia: Saunders. ISBN 1-4160-2973-7.
  5. ^ “UpToDate Inc.”.
  6. ^ Krause DC, Balish MF (February 2004). “Cellular engineering in a minimal microbe: structure and assembly of the terminal organelle of Mycoplasma pneumoniae”. Mol. Microbiol. 51 (4): 917–24. doi:10.1046/j.1365-2958.2003.03899.x. PMID 14763969.
  7. ^ Girard TD, Bernard GR (March 2007). “Mechanical ventilation in ARDS: a state-of-the-art review”. Chest 131 (3): 921–9. doi:10.1378/chest.06-1515. PMID 17356115.

November 26, 2010 - Posted by | Blood, Lungs | , ,

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