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Atypical Pneumonia

Last updated May 3, 2018

Pneumonia is an inflammation of the lungs, usually caused by an infection of the lung tissue.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Community-Acquired Pneumonia (causing Atypical Pneumonia)
  • Legionella pneumophila (causing Atypical Pneumonia)
  • Mycoplasma pneumoniae (causing Atypical Pneumonia) 

What is Atypical Pneumonia? (Definition/Background Information)

  • Atypical Pneumonia is a type of lung infection that is caused by specific types of bacteria namely, Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae.
  • Individuals with this infection often have mild signs and symptoms. They are able to carry on with their daily activities without much distress.
  • This infection is usually more prevalent during summer and autumn (fall) seasons and uncommon during winters. It can occur as a Community-Acquired Pneumonia.

Who gets Atypical Pneumonia? (Age and Sex Distribution)

  • Atypical Pneumonia can occur at any age; the affected age depends on the type of bacteria causing the condition
  • If the infection is caused by Mycoplasma pneumoniae bacteria, then it generally affects individuals under the age of 40 years
  • When caused by the bacteria Legionella pneumophila, it usually occurs in older individuals
  • Both males and females are affected
  • Atypical pneumonia is seen worldwide, in all races and ethnic groups. It is termed as Community-Acquired Pneumonia, and can cause local epidemics

What are the Risk Factors for Atypical Pneumonia? (Predisposing Factors)

The risk factors for Atypical Pneumonia include the following:

  • Chronic smoking, since smoking affects the immune system of the lungs
  • Individuals who suffer chronic illnesses and those who have weakened immune systems
  • Individuals on chronic steroidal therapy and immunosuppressive therapy
  • Those living in overcrowded spaces, such as dorms, other closed, ill-ventilated conditions; allows spread of the disease to more people
  • Atypical Pneumonia may be caused by Legionella pneumophila bacteria, which can grow in water bodies, such as water tanks. The use of this contaminated water in air conditioning units and humidifiers, can result in infecting individuals, who breathe in the infected humidified air

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Atypical Pneumonia? (Etiology)

  • Atypical Pneumonia is a bacterial infection caused by specific types of bacteria namely Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae, present in the lungs
  • This bacterial infection can spread from individual to individual through infected air droplets, when an infected person coughs or sneezes

What are the Signs and Symptoms of Atypical Pneumonia?

The signs and symptoms of Atypical Pneumonia include: 

  • In a majority of the individuals with the condition, the infection causes chills, cough, fever, and shortness of breath. Shortness of breath occurs when the individual is running, climbing up stairs, or swimming
  • Other symptoms that occur less commonly are: Chest pain, confusion (mostly in elderly individuals), headaches, lack of energy, hunger, joint stiffness, increased sweating
  • Symptoms that occur rarely include diarrhea, ear and eye pain, rashes, neck lumps, and sore throat
  • In general, the symptoms may improve after 4 days, but complete recovery takes about 2 weeks
  • Individuals with severe cases of Atypical Pneumonia, may take much longer to recover

How is Atypical Pneumonia Diagnosed?

A healthcare provider should have a high index of suspicion for Atypical Pneumonia. This is especially important since the signs and symptoms may not be very prominent. The following methods are used to diagnose the lung infection:

  • A through physical examination and complete medical history
  • Chest x-ray may reveal the presence of pneumonia
  • Arterial chest may indicate the level of oxygen in the blood. Atypical Pneumonia can affect the level of oxygen in blood, because of poor lung function
  • A complete blood count (CBC) reveals an increased amount of white blood cells, which is often a sign of infection
  • Sputum culture and blood cultures are helpful in determining the cause of pneumonia. It is important for the healthcare provider to communicate with the laboratory, the possibility of Atypical Pneumonia. This is especially important, since the bacteria causing the infection, requires special testing procedures in the laboratory
  • Bronchoscopy to help rule out other causes of pneumonia
  • CT scan of chest is also helpful in determining the extent of pneumonia
  • In severe cases of the lung infection, an open lung biopsy may be sometimes performed to rule out other causes

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis. 

What are the possible Complications of Atypical Pneumonia?

In a majority of the individuals Atypical Pneumonia does not cause any significant complications. However, in others, the complications could include:

  • Sometimes, Atypical Pneumonia can spread from the lungs to the brain, causing brain infection. This can result in severe headaches and confusion
  • Severe infections of the lung due to the disease can cause permanent lung damage, in some rare cases. In most of the individuals, no prominent lung damage is noted
  • Some individuals may have a condition called hemolytic anemia. This is because the Atypical Pneumonia bacteria can cause formation of autoantibodies, which destroys blood cells. The destruction of red blood cells results in anemia. Complete treatment of the condition will also result in resolution of hemolytic anemia 

How is Atypical Pneumonia Treated?

The following treatment measures are adopted to treat Atypical Pneumonia:

  • Antibiotic therapy is used as the main treatment course. Other treatments are used to alleviate pain, but they do not help in getting rid of the infection.
  • Over-the-counter medication for fever and cough can help improve one’s symptoms. It is important to note that taking any such over-the-counter medication, should only be after consulting your healthcare provider
  • Plenty of rest and fluids is advised, which will help in speeding recovery
  • In severe cases of Atypical Pneumonia, the lung function may be severely affected and oxygen treatment may be necessary

How can Atypical Pneumonia be Prevented?

The following preventative measures can help stop the spread of Atypical Pneumonia:

  • Frequently wash hands so as to not spread the bacteria
  • Avoid contact with individuals affected by the condition, where possible. This also includes avoiding visiting them in hospitals. This helps decrease the infection spread within the community
  • Annual flu vaccination shot may help in boosting one’s immune system

What is the Prognosis of Atypical Pneumonia? (Outcomes/Resolutions)

  • In a majority of individuals, Atypical Pneumonia resolves without any complications, and they recover completely within 2 weeks
  • Early diagnosis, complete rest, and appropriate antibiotic treatment, results in excellent prognosis
  • Individuals, in whom the condition is severe, it can result in permanent lung and brain damage
  • Most types of Atypical Pneumonia are not lethal, when the right antibiotics are used
  • Atypical Pneumonia caused by the bacteria Legionella pneumophila can be fatal, if the patient has a very poor immune system, severe diabetes, or severe kidney failure

Additional and Relevant Useful Information for Atypical Pneumonia:

Atypical Pneumonia should be distinguished from other types of pneumonia, since there are several types of them. Your healthcare provider will determine the cause and type of pneumonia through appropriate testing.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 21, 2013
Last updated: May 3, 2018

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