Walking pneumonia
Key points
- Atypical pneumonia refers to pneumonia caused by certain bacteria - namely, Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae.
- Atypical pneumonia due to Mycoplasma and Chlamydophila usually cause milder forms of pneumonia and are 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.
- 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.
- The mainstay of treatment for atypical pneumonia is antibiotic therapy.
Alternative names
Atypical pneumonia; Chlamydophila pneumoniae
Definition
Atypical pneumonia refers to pneumonia caused by certain bacteria - namely, 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, incidence, and risk factors
Atypical pneumonia due to Mycoplasma and Chlamydophila usually cause milder forms of pneumonia and are 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 may 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 individuals, 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) has also been associated with pneumonia due to Legionella.
Symptoms
- chills
- fevers
- cough - may be dry or produce phlegm
- headache
- muscular stiffness and aching
- breathing, rapid may be present
- shortness of breath may be present
- loss of appetite (anorexia)
- malaise
- confusion (especially with Legionella)
- rash (especially with Mycoplasma)
- diarrhea (especially with Legionella)
Signs and tests
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.
Written and revised by
David Cohen, M.D.
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