What is the clinical presentation of atypical community-acquired pneumonia (CAP) and which pathogens are involved?

Updated: Oct 31, 2019
  • Author: Stephanie L Baer, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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The clinical presentation of so-called “atypical” CAP is often subacute and frequently indolent. In addition, patients with atypical CAP may present with more subtle pulmonary findings, nonlobar infiltrates on radiography, and various extrapulmonary manifestations (eg, diarrhea, otalgia). Atypical CAP pathogens include the following:

  • Mycoplasma pneumoniae
  • Chlamydophila ( Chlamydia) pneumoniae
  • Legionella pneumophila (Legionnaires disease)
  • Respiratory viruses, including the following:
  • Influenza A and B
  • Rhinovirus
  • Respiratory syncytial virus
  • Human metapneumovirus
  • Adenovirus 4 and 7
  • Parainfluenza virus
  • Other rare CAP pathogens, include the following:
    • Viruses
      • Coxsackievirus
      • Echovirus
      • Coronavirus (MERS-CoV, SARS)
      • Hantavirus
      • Epstein-Barr virus
      • Cytomegalovirus
      • Herpes simplex virus
      • Human herpesvirus 6
      • Varicella-zoster virus
      • Metapneumovirus [5]
    • Bacteria
      • Chlamydophila psittaci (psittacosis)
      • Coxiella burnetii (Q fever)
      • Francisella tularensis (tularemia)
    • Mycobacteria
      • Mycobacteria tuberculosis
      • Nontuberculous mycobacteria (uncommon)
    • Endemic fungi (causing subacute or chronic pneumonia)
      • Histoplasma capsulatum
      • Cryptococcus neoformans neoformans and neoformans gattii
      • Coccidioides immitis

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