Pneumonia Types Atypical

While various types of pneumonia have different causes, all of them do trigger some degree of lung inflammation. Bacteria, chemicals in the air or any other inhaled irritant can all cause lung inflammation.

Although pneumonia has the potential to be a very serious and harmful illness, in some cases, it is mild and won’t severely affect a person’s day-to-day activities. By definition, atypical pneumonia is any form of pneumonia not caused by three specific bacteria.

Causes of Atypical Pneumonia

Atypical pneumonia is caused by one or more of the following organisms:

  • Chlamydophila pneumoniae
  • Legionella pneumophila
  • Mycoplasma pneumoniae.

Mycoplasma most commonly occurs in younger people and may cause symptoms outside of the lungs, such as skin rashes. Due to its physical structure, this organism can easily move past the protective layer within the respiratory system, making it very difficult for the body to clear out Mycoplasma on its own.

While Chlamydophila infections generally result in a milder form of pneumonia, Legionella can result in a much more serious disease that has high mortality rates.

Legionnaire’s Disease

In 1976, a famous outbreak of a particular kind of pneumonia, now known as Legionnaire’s Disease, infected hundreds of people. Just a few weeks after a celebration of the American bicentennial, hundreds of people (out of the thousands of American Legionnaires who gathered to participate in the celebration) fell seriously ill. Thirty-four people died.

Discovered six months later, the cause of the illness was the bacterium now called Legionella pneumophila. Researchers also discovered that most patients likely became infected through ingesting infected:

  • drinking water
  • soil
  • water vapor near showers, pools and air conditioners.

Since the 1976 epidemic, several other outbreaks of Legionnaire’s Disease have occurred in institutions around the world, including in hospitals, prisons and nursing homes. Anywhere in which a large number of people are concentrated in a small area can create a dangerous breeding ground for disease outbreak, including Legionnaire’s Disease.

Signs and Symptoms of Atypical Pneumonia

So, what are the signs and symptoms of atypical pneumonia? At the onset of atypical pneumonia, symptoms are often difficult to differentiate from those of the common cold. The following list provides several possible signs of atypical pneumonia:

  • chills
  • cough
  • fatigue
  • fever
  • headache
  • loss of appetite.

While patients may experience a variety of other symptoms, the above six are the most common signs of atypical pneumonia.

Risk Factors for Atypical Pneumonia

As with any infectious disease, anyone is at risk of developing atypical pneumonia. However, certain groups of people are at higher risk, including:

  • people with chronic illnesses
  • people with weakened immune systems (such as HIV patients)
  • smokers or others with damaged respiratory tracts
  • the elderly.

These people are particularly susceptible to an atypical pneumonia infection because their immune systems are not strong enough to fight off and kill infectious bacteria. Treatment for Atypical Pneumonia

A chest x-ray is often needed to make a proper pneumonia diagnosis. Once atypical pneumonia has been diagnosed, the most common treatment is antibiotics. People infected with this disease often find relief from their symptoms within a week of starting antibiotic treatment.

While antibiotics are effective at completely clearing up mild cases of atypical pneumonia, in more serious cases, relapse can occur after a course of antibiotics. If relapse occurs, doctors will likely perform a thorough physical exam to see if any other more serious medical conditions are causing recurring atypical pneumonia.


Cantu, Santos Jr., MD (2006). Pneumonia, Mycoplasma. Retrieved March 23, 2008, from the eMedicine Web site.

Grayson, Charlotte, MD (2006). Atypical Pneumonia. Retrieved March 23, 2008, from the University of Pennsylvania Health System Web site.

Mayo Clinic Staff (2006). Legionnaires’ Disease. Retrieved March 23, 2008, from the Mayo Clinic Web site.