Differentials
Atypical pneumonia caused by other pathogens
SIGNS / SYMPTOMS
There are no differentiating signs/symptoms.
INVESTIGATIONS
Serology, culture, or polymerase chain reaction is positive for organisms such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, or Legionella pneumophila.
Sepsis
SIGNS / SYMPTOMS
There are no differentiating signs/symptoms.
INVESTIGATIONS
Blood cultures are positive for gram-positive and gram-negative organisms, including facultative and fastidious organisms.
Infective endocarditis
SIGNS / SYMPTOMS
A history of intravenous drug use.
INVESTIGATIONS
Serial cultures are positive for typical bacteria such as Streptococcus and Staphylococcus; other organisms require special culture, such as Aspergillus, Brucella, Coxiella, and HACEK bacteria (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella species, and Kingella species).
Myocardial infarction
SIGNS / SYMPTOMS
Chest pain.
INVESTIGATIONS
The rise and fall of cardiac biomarkers such as troponin and creatine kinase are important in the diagnosis, as is a serial change in the electrocardiogram.
Tonsillitis
SIGNS / SYMPTOMS
There are no differentiating signs/symptoms.
INVESTIGATIONS
Oropharyngeal swab test is positive for group A and beta-hemolytic Streptococcus.
Hepatitis
SIGNS / SYMPTOMS
There are no differentiating signs/symptoms.
Can be caused by many different etiologies.
INVESTIGATIONS
Serology is positive for hepatitis A to E (>95% of viral causes), cytomegalovirus, or herpes simplex virus. Epstein-Barr virus is a less common case in the setting of systemic disease.
Fever of unknown origin
SIGNS / SYMPTOMS
A comprehensive history of exposure to others who are ill, travel to a tropical or developing country, and recent treatment.
Physical exam may reveal skin rash, lymphadenopathy, bites, or skin discoloration depending on the cause.
INVESTIGATIONS
Extensive testing is required and includes serology, blood cultures, and specialized tests for immune function.
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