What are the causes of a persistent sore throat lasting more than 2–3 weeks?

Causes of Persistent Sore Throat (>2-3 Weeks)

A sore throat persisting beyond 3 weeks mandates direct laryngoscopic examination because this duration exceeds the expected course of benign viral infections and raises concern for serious pathology including laryngeal cancer. 1

Expected Duration of Common Causes

Most benign causes resolve much earlier than 2-3 weeks:

• Viral pharyngitis: Resolves within 1 week, typically less than 7 days even without treatment 1
• Streptococcal pharyngitis: Symptoms resolve within 3-4 days even without antibiotics 1
• Viral laryngitis: Symptoms last 1-3 weeks maximum, representing the upper limit for benign viral causes 1
• Post-viral cough: May persist 3-8 weeks after upper respiratory infection, but sore throat itself should not persist this long 2

Major Causes of Persistent Sore Throat

Malignancy (Most Critical to Rule Out)

• Laryngeal cancer: Delays in diagnosis beyond 3 months lead to higher disease stage and worse prognosis 1
• Cough is the fourth most common presenting feature of lung cancer, which can cause persistent throat symptoms 2
• Unilateral symptoms, progressive worsening, and associated dysphagia are concerning features 1, 3

Chronic Infections

• Chronic Group A Streptococcus carrier state: These patients harbor the organism without active infection, don't benefit from antibiotics, and are at low risk for complications 2, 1
• Pertussis infection: Can cause persistent cough and throat symptoms; 10% of chronic cough cases had positive nasal swabs for Bordetella 2
• Tuberculosis or fungal infections: Particularly in immunocompromised patients 4

Gastroesophageal Reflux Disease (GERD)

• GERD is one of the main causes of chronic throat symptoms in specialist clinics 2
• Requires intensive acid suppression with proton pump inhibitors for minimum of 2 months 2

Upper Airway Cough Syndrome (UACS)

• Previously called post-nasal drip syndrome 2
• One of the most common causes of chronic cough and throat irritation in specialist settings 2

Chronic Inflammatory Conditions

• Eosinophilic bronchitis: Can present with persistent throat clearing and irritation 2
• Chronic rhinosinusitis: Causes persistent throat symptoms from post-nasal drainage 2

Rare but Serious Bacterial Infections

• Fusobacterium necrophorum: Implicated in 10-20% of endemic pharyngitis in adolescents and can progress to Lemierre syndrome 2
• Groups C and G streptococci: Can cause severe or recurrent pharyngitis with complications including reactive arthritis and glomerulonephritis 2

Non-Infectious Causes

• Thyroiditis: Relatively uncommon but important consideration 4
• Neoplastic processes: Including lymphoma and other head/neck malignancies 3
• Chronic irritation: From smoking, environmental exposures, or vocal strain 2

Mandatory Evaluation Approach

For sore throat lasting beyond 3 weeks, laryngoscopy is necessary to directly visualize the larynx and pharynx. 1 Transnasal flexible fiberoptic laryngoscopy is the standard office procedure 1.

Additional baseline investigations should include:

• Chest radiography: Mandatory in evaluation of chronic symptoms to rule out malignancy and other pulmonary pathology 2
• Spirometry: Should be performed to assess for underlying airway disease 2

Critical Red Flags Requiring Immediate Evaluation

• Unilateral tonsillar swelling with uvular deviation: Suggests peritonsillar abscess 1
• Persistent high fever with severe pharyngitis in adolescents/young adults: Consider Lemierre syndrome 2, 1
• Difficulty swallowing, drooling, neck tenderness or swelling: Evaluate urgently for peritonsillar abscess, retropharyngeal abscess, or epiglottitis 2
• Progressive worsening rather than improvement: Concerning for malignancy or serious infection 1

Common Pitfalls to Avoid

• Assuming all persistent sore throats are "slow to resolve" viral infections: This delays diagnosis of serious conditions like cancer 1
• Continuing to prescribe antibiotics without proper evaluation: Over 60% of adults with sore throat receive unnecessary antibiotics 2, 1
• Waiting the full 3 months before laryngoscopy: A 1-month duration already exceeds typical viral illness and warrants earlier assessment, especially with concerning features 1
• Treating chronic streptococcal carriers with repeated antibiotic courses: These patients don't benefit from treatment 2, 1