Legionellosis differential diagnosis

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

Overview

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

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.

Disease	Clinical manifestation	Lab findings	Imaging findings	Chest X-ray
Legionnaires' disease	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	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	Dry cough Pleuritic chest pain Inflamed, opaque, hypomobile tympanic membrane	Lymphocytosis Cold agglutinins positive Positive Coombs 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	No specific clinical features of chlamydia pneumonia. Gradual symptoms 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