Legionellosis differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Ogechukwu Hannah Nnabude, MD

## Overview

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Legionnaires' disease must be differentiated from other causes of fever, dyspnea, cough, and sputum production, such as bacterial pneumonia, viral pneumonia, and other causes of atypical pneumonia.

## Differential Diagnosis

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Legionnaires' disease must be differentiated from other causes of fever, dyspnea, cough, and sputum production, such as bacterial pneumonia, viral pneumonia, and other causes of atypical pneumonia.[1]

Disease  | Clinical manifestation  | Lab findings  | Imaging findings  | Chest X-ray

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|
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Legionnaires' disease [2] [3] [4] |

* Dry cough
* High grade fever
* Bronchial breath sounds
* Asthenia
* Progressive dyspnea
* diarrhea
* Seizures and other neurological findings
* nausea, and vomiting
* Adult respiratory distress syndrome

* Legionella urinary antigen positive
* Leukocytosis with relative lymphopenia
* Hyponatremia
* Hypophosphatemia

* Alveolar consolidation on chest radiograph
* Lobar consolidation on chest radiograph

|  Chest X-ray of a patient with Legionnaires disease courtesy Hellerhoff
Q fever [5] [6] |

* Fever
* Dry cough
* Dyspnea
* Pleuritic chest pain
* myalgia
* headache

* Antibody detection using indirect immunofluorescence (IIF)
* PCR
* C. burnetii cultivated on special media such as embryonated eggs or cell culture
* A two-to-three fold increase in AST and ALT

Multiple soft infiltrative shadows on CXR

|  Q fever pneumonia - Case courtesy of Royal Melbourne Hospital Respiratory, Radiopaedia.org, rID 21993
Mycoplasma pneumonia [7] [8] |

* Dry cough
* Fever
* Pharyngitis
* Nausea and vomiting
* Sinus congestion
* Pleuritic chest pain
* Inflamed, opaque, hypomobile tympanic membrane

* Lymphocytosis
* Cold agglutinins positive
* Positive CoNombs test
* Leukocytosis
* Thrombocytosis

* Alveolar consolidation on chest radiograph
* Interstitial infiltrate on chest radiograph
* Lobar consolidation on chest radiograph

|  Mycoplasma pneumonia - Case courtesy of Dr Alborz Jahangiri, Radiopaedia.org, rID 45781
Chlamydia pneumonia |

* Associated with upper respiratory tract symptoms
* Associated with extrapulmonary maifestations such as:
* Meningitis
* Guillain-Barre syndrome

* Normal WBC count
* Positive antichlamydial antibody

|  |  Chlamydia-pneumonia - Case courtesy of Dr Andrew Dixon, Radiopaedia.org, rID 14567
Acute interstitial pneumonia |

* Dry cough
* Progressive dyspnea

* Nonspecific

* Disseminated consolidation on chest radiograph
* Interstitial infiltrate on chest radiograph
* Increased uptake on gallium scan

|  Acute Interstitial Pneumonitis Chest X-ray - Case Courtesy of Dr Salam, Radiopaedia, rID 45404
Pneumococcal pneumonia |

* High grade fever
* Hemoptysis
* Fine rales
* Pleuritic chest pain
* Increased breath sounds
* Bronchial breath sounds
* Dullness on chest percussion
* Purulent sputum
* Shallow respiration
* Pectoriloquy
* Increased tactile fremitus
* Productive cough
* Egophony

* Gram positive diplococci on sputum Gram stain
* Pleural effusion (exudative)
* Respiratory alkalosis

* Parenchymal hyperlucency on chest radiograph
* Increased uptake on gallium scan
* Unilateral diaphragm elevation on chest radiograph
* Alveolar consolidation on chest radiograph
* Lobar consolidation on chest radiograph

|  Chest X-ray of a patient with pneumococcal pneumonia - case courtesy Dr Jack Ren, Radiopaedia.org, rID 29090
Pneumocystis carinii pneumonia |

* Immunosuppressive state
* Subcutaneous emphysema
* Hacking cough
* Progressive dyspnea

* Respiratory alkalosis
* Serum beta-D-glucan elevation

* Alveolar consolidation on chest radiograph
* Lobar consolidation on chest radiograph
* Interstitial infiltrate on chest radiograph
* Pneumomediastinum on chest radiograph

|  Pneumocystis Jiroverci Chest Xray - Case Courtesy of Dr Behrang Amini, Radiopaedia, rID 1901
Pulmonary embolism |

* Calf pain or swelling
* Decreased pulse pressure
* Dyspnea
* Hemoptysis
* Hyperventilation
* Immobility
* Increased pulmonic component of heart sound
* Pleuritic chest pain
* Prior DVT
* Pulmonary hypertension
* Right ventricular heave
* Right-to-left shunt
* Substernal chest pain
* Tachypnea
* Thrombophlebitis
* Venous stasis
* Bone fracture

* D-dimer elevation
* Hypocapnia
* Hypoxia
* Pleural effusion (exudative or bloody)
* Atrial fibrillation on ECG
* Right axis deviation on ECG
* Right ventricular overload on ECG

* Normal chest radiograph
* Atelectasis on chest radiograph
* Lobar consolidation on chest radiograph
* Prominent pulmonary artery on chest radiograph
* Hampton's hump on chest radiograph
* Right ventricular enlargement on echocardiography
* Thrombus on echocardiography
* Segmental perfusion defect on lung scan
* V/Q mismatch on lung scan

|  Hampton Hump in a patient with pulmonary embolism courtesy of Hellerhoff
Viral pneumonia |

* Pleuritic chest pain
* Bronchial breath sounds
* Recent influenza
* Fine rales
* Bronchovesicular breath sounds

* Lymphocytosis
* Respiratory alkalosis

* Lobar consolidation on chest radiograph
* Interstitial infiltrate on chest radiograph

## References

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1. ↑ Irfan M, Farooqi J, Hasan R (2013). "Community-acquired pneumonia". Curr Opin Pulm Med. 19 (3): 198–208. doi:10.1097/MCP.0b013e32835f1d12. PMID 23422417.
2. ↑ Cunha BA, Burillo A, Bouza E (2016). "Legionnaires' disease". Lancet. 387 (10016): 376–385. doi:10.1016/S0140-6736(15)60078-2. PMID 26231463.CS1 maint: Multiple names: authors list (link)
3. ↑ Cunha BA, Cunha CB (2017). "Legionnaire's Disease: A Clinical Diagnostic Approach". Infect Dis Clin North Am. 31 (1): 81–93. doi:10.1016/j.idc.2016.10.007. PMID 28159178.
4. ↑ Chahin A, Opal SM (2017). "Severe Pneumonia Caused by Legionella pneumophila: Differential Diagnosis and Therapeutic Considerations". Infect Dis Clin North Am. 31 (1): 111–121. doi:10.1016/j.idc.2016.10.009. PMC 7135102 Check `|pmc=` value (help). PMID 28159171.
5. ↑ Okimoto N, Asaoka N, Osaki K, Kurihara T, Yamato K, Sunagawa T; et al. (2004). "Clinical features of Q fever pneumonia". Respirology. 9 (2): 278–82. doi:10.1111/j.1440-1843.2004.00586.x. PMID 15182283.CS1 maint: Multiple names: authors list (link)
6. ↑ Caron F, Meurice JC, Ingrand P, Bourgoin A, Masson P, Roblot P; et al. (1998). "Acute Q fever pneumonia: a review of 80 hospitalized patients". Chest. 114 (3): 808–13. doi:10.1378/chest.114.3.808. PMID 9743171.CS1 maint: Multiple names: authors list (link)
7. ↑ Parrott GL, Kinjo T, Fujita J (2016). "A Compendium for Mycoplasma pneumoniae". Front Microbiol. 7: 513. doi:10.3389/fmicb.2016.00513. PMC 4828434. PMID 27148202.CS1 maint: Multiple names: authors list (link)
8. ↑ Saraya T (2017). "Mycoplasma pneumoniae infection: Basics". J Gen Fam Med. 18 (3): 118–125. doi:10.1002/jgf2.15. PMC 5689399. PMID 29264006.