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Atypical Pneumonia

What is Atypical pneumonia? Atypical pneumonia refers to pneumonia caused by certain bacteria, such as, Legionella pneumophila, Mycoplasma pneumoniae and Chlamydophila pneumoniae.

While atypical pneumonias are commonly associated with milder forms of pneumonia, pneumonia due to Legionella, in particular, can be quite severe and lead to high mortality rates.

Causes of Atypical Pneumonia

Atypical pneumonia due to Mycoplasma and Chlamydophila usually cause milder forms of pneumonia and characterized by a more drawn out course of symptoms unlike other forms of pneumonia which can come on more quickly with more severe early symptoms.

Mycoplasma pneumonia often affects younger people and can be associated with symptoms outside of the lungs, such as anemia and rashes, and neurological syndromes such as meningitis, myelitis, and encephalitis. Severe forms of Mycoplasma pneumonia have been described in all age groups.

Chlamydophila pneumonia occurs year round and accounts for 5-15% of all pneumonias. It is usually mild with a low mortality rate. In contrast, atypical pneumonia due to Legionella accounts for 2-6% of pneumonias and has a higher mortality rate.

Elderly people, smokers, and people with chronic illnesses and weakened immune systems are at higher risk for this type of pneumonia. Contact with contaminated aerosol systems, like infected air conditioning systems have also been associated with pneumonia due to Legionella.

Symptoms for Atypical Pneumonia

Muscle stiffness and aching
Rapid breathing
Shortness of breath
Loss of appetite
Confusion . . .especially with Legionella
Rash . . . especially with Mycoplasma
Diarrhea . . . especially with Legionella

Exams and Tests for Atypical Pneumonia

People with suspected pneumonia should undergo a medical evaluation, including a thorough physical exam and a chest x-ray, especially since the physical exam may not always distinguish pneumonia from acute bronchitis or other respiratory infections.

Depending on the severity of illness, additional studies, such as a complete blood count, blood cultures, and sputum cultures, may be obtained.

When certain forms of atypical pneumonia are suspected, tests of your urine or a throat swab may be ordered as well.

Treatment for Atypical Pneumonia

The mainstay of treatment for atypical pneumonia is antibiotic therapy. In mild cases, treatment with oral antibiotics at home may be appropriate. Severe cases, which is common with pneumonia caused by Legionella may require intravenous antibiotics and oxygen supplementation.

Antibiotics with activity against these organisms include -- erythromycin, azithromycin, clarithromycin, fluoroquinolones and their derivatives (such as levofloxacin), and tetracyclines (such as doxycycline).

Outlook/Prognosis for Atypical Pneumonia

Most patients with pneumonia due to Mycoplasma or Chlamydophila do well with appropriate antibiotic therapy, although there is a small chance of relapse if antibiotics are used for too short a period of time, which is less than two weeks.

In the case of pneumonia due to Legionella, severe illness occurs particularly among the elderly and those with chronic diseases and weakened immune systems. It is associated with a higher mortality rate.

Possible Complications of Atypical Pneumonia

When to Contact a Medical Professional

Seek medical evaluation if you develop fevers, cough, and/or shortness of breath. While there are numerous causes for these symptoms, you will need to be evaluated for pneumonia.

Prevention of Atypical Pneumonia

There are no proven methods for preventing atypical pneumonia, and no vaccinations are available at this time for atypical pneumonias.