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Atypical pneumonia

  • Overview
  • Theory
  • Diagnosis
  • Management
  • Follow up
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Last reviewed: 1 Sep 2025
Last updated: 10 Sep 2024

Summary

Definition

History and exam

Key diagnostic factors

  • age <50 years
  • persistent cough
  • dry cough
  • long duration of symptoms
Full details

Other diagnostic factors

  • recent community exposure
  • throat involvement
  • fever
  • headache
  • diarrhea
  • bullous myringitis
  • lung rales/crepitations
  • rash
Full details

Risk factors

  • close community settings
  • immunosuppression
  • cigarette smoking
  • chronic lung disease
  • travel
  • male sex
  • immunomodulating drugs
Full details

Diagnostic investigations

1st investigations to order

  • oxygen saturation in air
  • WBC count
  • hemoglobin
  • Liver function tests (LFTs)
  • BUN level
  • real-time reverse transcription polymerase chain reaction (RT-PCR) for SARS-CoV-2
  • chest x-ray
Full details

Investigations to consider

  • urinary Legionella antigen
  • sputum culture
  • molecular diagnosis of Mycoplasma pneumoniae or Chlamydophila pneumoniae
  • nasopharyngeal PCR
Full details

Treatment algorithm

ACUTE

presumed atypical bacterial pneumonia: nonpregnant adult

presumed atypical bacterial pneumonia: pregnant or child

Contributors

Authors

Lorenzo Di Francesco, MD, SFHM, FACP

Professor of Medicine

Department of Medicine

Division of General Internal Medicine

Emory University School of Medicine

GA

Disclosures

LDF is a Gen Medicine/Point of Care Editorial Board Member for ClinicalKey.

Peer reviewers

Mark Woodhead, BSc, DM, FRCP

Honorary Senior Lecturer (University of Manchester)

Consultant in General & Respiratory Medicine

Department of Respiratory Medicine

Manchester Royal Infirmary

Manchester

UK

Disclosures

MW is an author of a reference cited in this topic.

Ethan Rubinstein, MD

H.E. Sellers Research Chair in Infectious Diseases

Head

Section of Adult Infectious Diseases

Department of Internal Medicine

Department of Medical Microbiology

University of Manitoba

Winnipeg

Canada

Disclosures

At the time of the peer review, Professor Rubinstein declared no competing interests. We were made aware that Professor Rubinstein is now deceased.

George L. Anesi, MD, MSCE, MBE

​Assistant Professor

Medicine, Division of Pulmonary, Allergy, and Critical Care

Perelman School of Medicine

University of Pennsylvania

PA

Disclosures

GLA receives research funding from the National Institutes of Health (K23HL161353), the CDC Foundation, the Society of Critical Care Medicine (SCCM), and the University of Pennsylvania Perelman School of Medicine Thomas B. McCabe and Jeannette E. Laws McCabe Fund. GLA reports payments for authoring chapters for UpToDate and for expert witness consulting, including involving COVID-19, and reports that his spouse is employed by the U.S. Food and Drug Administration (FDA).

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia: an official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-67.Full text  Abstract

Lim WS, Baudouin SV, George RC, et al; Pneumonia Guidelines Committee of the BTS Standards of Care Committee. BTS guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax. 2009 Oct;64 Suppl 3:iii1-55.Full text  Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

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