Q fever differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Ahmed Younes M.B.B.CH [2]

Overview

Q fever must be differentiated from other diseases that cause atypical pneumonia such as mycoplasma pneumonia and legionella pneumonia.

Differentiating Q fever from other diseases

Q fever must be differentiated from other diseases that cause atypical pneumonia such as mycoplasma pneumonia and legionella pneumonia.

Disease	Prominent clinical features	Lab findings	Chest X ray
Q fever	Q fever is characterized by abrupt onset of fever, myalgia, headache and other constitutional symptoms. Cough is the most prominent respiratory symptom and it is usually dry. Cough is associated with dyspnea and pleuritic chest pain.	Antibody detection using Indirect immunofluorescence (IIF) is the preferred method for diagnosis. PCR can be used if IIF is negative or very early once disease is suspected. C. burnetii does not grow on ordinary blood cultures but can be cultivated on special media as embryonated eggs or cell culture. Two to three fold increase in AST and ALT is seen in most of the patients.	Q fever pneumonia - - Case courtesy of Royal Melbourne Hospital Respiratory, Radiopaedia.org, rID 21993
Mycoplasma pneumonia	Mycoplasma pneumonia can be asymptomatic Headache, nausea and malaise usually precede the onset of symptoms Cough which is intractable and nonproductive	Postitve Coomb’s test Leukocytosis Thrombocytosis	Mycoplasma pneumonia - Case courtesy of Dr Alborz Jahangiri, Radiopaedia.org, rID 45781
Legionellosis	Legionella pneumonia is characterized by cough that is slightly productive Constitutional symptoms such as chills, myalgia, arthralgia Gastrointestinal symptoms such as diarrhea, nausea and vomiting.	Labs are non specific for diagnosing legionella pneumonia Renal and hepatic dysfunction Thrombocytopenia and leukocytosis Hyponatremia	Legionella pneumonia - Case courtesy of Dr Henry Knipe, Radiopaedia.org, rID 31816
Chlamydia pneumonia	There are no specific clinical features for chlamydia pneumonia. Symptoms appear gradually. Chlamydia infection is usually associated with upper respiratory tract symptoms (pharyngitis, sinusitis, etc). It might be associated with extrapulmonary manifestaions as meningitis and Guillain-Barre syndrome.	Chlamydia pneumonia is usually associated with normal WBC count. It's diagnosed with the presence of antichlamydial antibody (through complement fixation or direct immunofluoroscence) or direct antigen detection.	Chlamydia-pneumonia - Case courtesy of Dr Andrew Dixon, Radiopaedia.org, rID 14567

Table 1; Differentiating psittacosis from other diseases

Clinical feature	Cough	Sputum	Dyspnea	Sore throat	Headache	Confusion	Diarrhea	Chest radiograph changes	Hyponatremia	Leukopenia	Abnormal Liver function tests	Treatment
Psittacosis	++	-	+	-	+++	+	Minimal	No changes seen	-	+	-	Doxycycline
C.pneumoniae pneumonia	+	+	+	+++	++	+	-	Minimal changes observed	-	-	-	Doxycycline, Azithromycin
M. pneumoniae pneumonia	++	++	++	-	-	-	-	Bronchial wall thickening Centrilobular nodules Ground-glass attenuation Consolidation	-	-	+	Doxycycline
L. Pneumophila infection	+	+++	+++	-	+	++	+	Often Multifocal	++	+	++	Doxycycline
Influenza	++	++	++	++	++	+/-	+/-	Bi-basal air-space opacities Perihilar reticular and alveolar infiltrates	-	-	-	zanamivir, oseltamivir,
Endocarditis	++	++	+	-	-	-	-	Hazy opacities at lung bases bilaterally	-	+/-	+/-	Vancomycin
Coxiella burnetii infection	++	-	+	+/-	-	+/-	Minimal	Segmental or lobar opacification Occasional pleural effusions	-	+/-	=/-	Doxycycline
Leptospirosis	++	+	++	+	+	++	-	Multiple ill-defined nodules in both lungs.	+++			Doxycycline, azithromycin, amoxicillin
Brucellosis	++	-	+	-	++	+	-	Soft miliary mottling Parenchymal nodules Consolidation Chronic diffuse changes Hilar or paratracheal lymphadenopathy Pneumothorax.	-/+	+/-	+/-	Doxycycline, rifampin

Key;

+, occurs in some cases

++, occurs in many cases,

+++, occurs frequently

References

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