What are the causes of pharyngitis?

Causes of Pharyngitis

Viruses are the most common cause of pharyngitis, while Group A β-hemolytic streptococci (GAS) represent the most important bacterial cause requiring specific treatment to prevent complications. 1

Viral Causes (Most Common)

• Respiratory viruses:

  • Adenovirus
  • Influenza virus
  • Parainfluenza virus
  • Rhinovirus
  • Respiratory syncytial virus (RSV)

• Other viral agents:

  • Coxsackievirus
  • Echoviruses
  • Herpes simplex virus
  • Epstein-Barr virus (often with infectious mononucleosis features)
  • Cytomegalovirus
  • Rubella virus
  • Measles virus
  • Human metapneumovirus
  • Human bocavirus 1

Bacterial Causes

• Group A β-hemolytic streptococci (GAS) - Most common and clinically significant bacterial cause

  • Primarily affects children 5-15 years old
  • More common in winter and early spring
  • Only common form requiring antibiotic therapy 1

• Other streptococcal groups:

  • Group C streptococci - relatively common in college students and adults
  • Group G streptococci - less established role in endemic pharyngitis 1

• Other bacterial pathogens:

  • Arcanobacterium haemolyticum - rare, more common in teenagers/young adults
  • Neisseria gonorrhoeae - in sexually active individuals
  • Corynebacterium diphtheriae - rare but serious
  • Fusobacterium necrophorum - emerging pathogen in adolescents and young adults
  • Francisella tularensis - rare
  • Yersinia enterocolitica - rare
  • Mixed anaerobic bacteria (Vincent's angina) - rare 1

Atypical Pathogens

• Mycoplasma pneumoniae - uncommon
• Chlamydophila (Chlamydia) pneumoniae - uncommon 1

Clinical Features Suggesting Specific Etiologies

Features suggesting GAS pharyngitis:

• Sudden onset
• Sore throat
• Fever
• Headache
• Nausea, vomiting, abdominal pain (especially in children)
• Tonsillopharyngeal erythema with/without exudates
• Tender enlarged anterior cervical nodes
• Palatal petechiae
• Scarlatiniform rash 1

Features suggesting viral etiology:

• Conjunctivitis
• Coryza (nasal congestion/discharge)
• Cough
• Hoarseness
• Diarrhea
• Discrete ulcerative lesions
• Viral exanthem 1

Diagnostic Approach

For suspected GAS pharyngitis, throat culture or rapid antigen detection test is recommended, particularly in patients with:

• Persistent fever
• Tonsillar exudates
• Tender anterior cervical adenopathy
• Absence of cough 1

Complications of Untreated Pharyngitis

• GAS pharyngitis complications:
  • Acute rheumatic fever
  • Post-streptococcal glomerulonephritis
  • Peritonsillar abscess
  • Rarely, pulmonary-renal syndrome 2

Treatment Considerations

• Viral pharyngitis: Supportive care only
• GAS pharyngitis: Antibiotic therapy (penicillin is first-line)
• Other bacterial causes: Treatment varies by pathogen, but most non-GAS bacterial pharyngitis does not have proven benefit from antibiotics 1

Important Clinical Pitfalls

1. Overdiagnosis of bacterial pharyngitis: Most cases are viral and do not require antibiotics. Inappropriate antibiotic use contributes to antimicrobial resistance.

2. Missing GAS pharyngitis: Clinical features alone cannot reliably diagnose GAS pharyngitis; laboratory confirmation is necessary.

3. Overlooking rare but serious causes: Conditions like Lemierre syndrome (associated with F. necrophorum) require urgent diagnosis and treatment.

4. Failure to recognize EBV-related pharyngitis: May present with more systemic symptoms and requires different management approaches 3.

5. Ignoring potential complications: Untreated GAS pharyngitis can lead to serious sequelae including acute rheumatic fever and post-streptococcal glomerulonephritis 2.