Differential Diagnoses for Sore Throat
Primary Etiologic Categories
The vast majority (65-85%) of acute sore throat cases are viral in origin, with bacterial causes—primarily Group A β-hemolytic streptococcus (GABHS)—accounting for only 15-30% in children and 5-15% in adults. 1, 2
Viral Causes (Most Common)
- Respiratory viruses including rhinovirus, coronavirus, adenovirus, influenza, parainfluenza, and respiratory syncytial virus are the most frequent causes 3, 1
- Epstein-Barr virus causes infectious mononucleosis with pharyngitis accompanied by generalized lymphadenopathy and splenomegaly 3
- Herpes simplex virus and coxsackievirus (causing herpangina with characteristic vesicles) 3, 4
- Cytomegalovirus, rubella virus, and measles virus can cause pharyngitis as part of systemic infections 3
Bacterial Causes
Common Bacterial Pathogens
- Group A β-hemolytic streptococcus (Streptococcus pyogenes) is the most common bacterial cause requiring antibiotic therapy 3
- Groups C and G β-hemolytic streptococci can cause pharyngitis with milder clinical presentation 3
Less Common Bacterial Pathogens
- Corynebacterium diphtheriae presents with characteristic membrane formation 3, 4
- Neisseria gonorrhoeae causes pharyngitis in sexually active individuals, often with infection at other sites 3, 4
- Arcanobacterium haemolyticum causes pharyngitis with scarlet fever-like rash, particularly in teenagers and young adults 3
- Mycoplasma pneumoniae and Chlamydia pneumoniae are uncommon causes, often associated with atypical pneumonia 3, 4
- Francisella tularensis and Yersinia enterocolitica are rare bacterial causes 3
- Mixed anaerobic infections (Vincent's angina) 3
- Haemophilus influenzae type b may present with cherry-red epiglottis 4
Fungal Causes
- Candida species causing oropharyngeal candidiasis, which should prompt consideration of HIV infection or immunosuppression 4, 5
Complicated/Suppurative Conditions
- Peritonsillar abscess (quinsy) is a polymicrobial infection occurring mainly in young adults 3, 4
- Retropharyngeal abscess requires surgical drainage 4, 6
- Epiglottitis is life-threatening and requires aggressive early airway management 6
- Lemierre disease (suppurative thrombophlebitis of internal jugular vein) 3
Non-Infectious Causes
- Thyroiditis is a relatively uncommon but important non-infectious consideration 4
- Tonsillar cancer should be considered with persistent symptoms 7
- Hematologic disorders may present with pharyngeal manifestations (as evidenced by cases with lymphocyte and platelet abnormalities) 5
Clinical Clues for Differentiation
Viral pharyngitis is strongly suggested by: conjunctivitis, cough, hoarseness, coryza, diarrhea, anterior stomatitis, discrete ulcerative lesions, or viral exanthem 3, 1
GABHS pharyngitis is suggested by: sudden-onset sore throat, fever, tonsillar exudates, tender anterior cervical adenopathy, absence of cough, and patient age 5-15 years 3, 1
Critical Pitfall to Avoid
The most common diagnostic error is failing to recognize that clinical features alone cannot reliably distinguish GABHS from viral pharyngitis—microbiological confirmation with throat culture or rapid antigen testing is required when GABHS is suspected based on clinical scoring systems like the Centor criteria 3, 1