Atypical pneumonia

Atypical pneumonia is often due to Mycoplasma or Chlamydia infections when the pneumonia is community-acquired. This type of atypical pneumonia responds well to macrolide antibiotics. In this week's issue of the New England Journal of Medicine (article), there is a report about a healthy young woman who developed a form of atypical pneumonia that rapidly progressed to respiratory failure. Hence this is a good opportunity to discuss some clinical aspects of severe atypical pneumonia acquired from the community.

Atypical pneumonia - other than Mycoplasma and Chlamydia - should be suspected when the respiratory illness does not respond to treatment with the usual antibiotics for community acquired pneumonia.

1. Think of Legionella pneumophilia when there are associated symptoms and signs of involvement of the CNS and / or gastrointestinal tract.

2. Think of Leptospiral infection when there is associated severe myalgia, headache or neck pain. Involvement of the liver and kidney and the presence of a skin rash are further points in favour of suspecting this condition.

3. Think of fungal pneumonia if the patient is immunocompromised and if there is exposure to an enviroment where fungi are likely - mouldy and damp places like caves, for example.  

4. Think of Toxoplasma and Pasteurella infections if there is close exposure to cats.

5. Think of Lyme disease, Rickettsial infections and Tularemia if there is a history or physical evidence of tick bites.