What is the differential diagnosis and treatment approach for tonsillitis in a child or young adult with no significant medical history?

Differential Diagnosis of Tonsillitis

The differential diagnosis of tonsillitis must distinguish between viral causes (70-95% of cases), Group A β-hemolytic streptococcus (GABHS) bacterial infection (15-30% in children 5-15 years, 5-15% in adults), and less common but potentially life-threatening bacterial pathogens. 1, 2

Primary Diagnostic Categories

Viral Tonsillitis (Most Common)

• Accounts for 70-95% of all tonsillitis cases 2, 3
• Common viral pathogens include:
  • Rhinovirus, coronavirus, adenovirus 4, 1
  • Epstein-Barr virus (infectious mononucleosis) 4, 1
  • Herpes simplex virus, cytomegalovirus 1
  • Influenza, parainfluenza, respiratory syncytial virus 4
  • Enteroviruses 4
• Clinical features suggesting viral etiology: coryza, hoarseness, cough, conjunctivitis, diarrhea, or characteristic oral ulcers/vesicles 4, 1

Group A β-Hemolytic Streptococcus (GABHS) - Most Important Bacterial Cause

• Represents 15-30% of tonsillitis in children aged 5-15 years and 5-15% in adults 1, 2
• Must be identified and treated due to risk of serious complications:
  • Acute rheumatic fever 4
  • Acute glomerulonephritis 1, 2
  • Peritonsillar abscess 4
  • Cervical lymphadenitis, mastoiditis 4
  • Scarlet fever 1
• Classic presentation includes sudden-onset sore throat, fever >38.3°C (101°F), tonsillar exudates, tender anterior cervical adenopathy, and absence of cough 4, 5

Other Bacterial Pathogens (Less Common)

• Groups C and G β-hemolytic streptococci 4, 1
• Fusobacterium necrophorum - particularly important in adolescents and young adults, can cause Lemierre syndrome (life-threatening septic thrombophlebitis of internal jugular vein) 1
• Arcanobacterium haemolyticum 4, 1
• Neisseria gonorrhoeae (consider in sexually active patients) 4, 1
• Mycoplasma pneumoniae and Chlamydia pneumoniae 4, 1
• Corynebacterium diphtheriae (rare, consider in unvaccinated patients with membranous tonsillitis) 4

Life-Threatening Complications to Exclude Immediately

Any patient with unusually severe presentation requires urgent evaluation for the following conditions: 1

• Peritonsillar abscess - unilateral tonsillar swelling, uvular deviation, trismus, "hot potato" voice 1
• Parapharyngeal abscess - neck swelling, torticollis, systemic toxicity 1
• Epiglottitis - drooling, stridor, tripod positioning, respiratory distress 1
• Lemierre syndrome - severe pharyngitis followed by neck pain/swelling, septic emboli 1

Algorithmic Diagnostic Approach

Step 1: Clinical Assessment Using Modified Centor Criteria

Use the Centor criteria to stratify probability of GABHS infection: 1, 5

Award 1 point for each:

• Fever by history 1
• Tonsillar exudates 1
• Tender anterior cervical adenopathy 1
• Absence of cough 1

Interpretation:

• Score 0-2: Low probability of GABHS - no testing or antibiotics needed 1
• Score 3-4: High probability of GABHS - perform rapid antigen detection test (RADT) and/or throat culture 1, 5

Step 2: Microbiologic Confirmation (When Indicated)

• Perform RADT and/or throat culture before initiating antibiotics in patients with Centor score ≥3 6, 5
• Throat swab technique: vigorously swab both tonsils and posterior pharynx 4
• Culture on sheep blood agar remains the gold standard; if RADT negative but clinical suspicion high, confirm with culture 4
• At least 10 colonies of GABHS should be present for positive diagnosis 4

Step 3: Red Flag Assessment

Immediately evaluate for suppurative complications if patient has: 1

• Difficulty swallowing or drooling 1
• Neck tenderness or swelling 1
• Airway obstruction symptoms 1
• Unilateral tonsillar swelling 1
• Severe systemic toxicity 1

Treatment Based on Etiology

Confirmed GABHS Tonsillitis

• Penicillin V for 10 days is first-line therapy 4, 6, 5
• Amoxicillin for 10 days is an acceptable alternative 6, 5
• For penicillin-allergic patients (non-anaphylactic): first-generation cephalosporins 5
• For penicillin-allergic patients (anaphylactic): clindamycin, azithromycin, or clarithromycin 5, 7
• The full 10-day course is mandatory to prevent rheumatic fever and maximize bacterial eradication 6, 5

Viral Tonsillitis

• Supportive care only - no antibiotics 6
• Ibuprofen, acetaminophen, or both for pain control 6
• Adequate hydration and rest 6

Treatment Failures or Recurrent GABHS

• For documented treatment failures: amoxicillin-clavulanate, clindamycin, or second/third-generation cephalosporins 4, 5
• These agents are effective against β-lactamase-producing bacteria that may "shield" GABHS from penicillin 4, 8

Critical Pitfalls to Avoid

• Never prescribe antibiotics without confirming bacterial infection through testing - this leads to inappropriate antibiotic use and resistance 6, 5
• Never use antibiotic courses shorter than 10 days for confirmed GABHS - increases treatment failure risk and does not prevent rheumatic fever 4, 6
• Never use broad-spectrum antibiotics when narrow-spectrum penicillins are effective - contributes to antibiotic resistance 6
• Do not obtain post-treatment cultures in asymptomatic patients who completed appropriate therapy - not recommended 4, 5
• Do not treat asymptomatic household contacts - routine testing not recommended 4

Indications for Tonsillectomy

Consider tonsillectomy for recurrent tonsillitis meeting Paradise criteria: 4, 6

• ≥7 documented episodes in the preceding year, OR
• ≥5 documented episodes per year for 2 consecutive years, OR
• ≥3 documented episodes per year for 3 consecutive years

Each episode must be documented with: 4

• Temperature >38.3°C (101°F) 4
• Cervical adenopathy 4
• Tonsillar exudate 4
• Positive test for GABHS 4

Watchful waiting is strongly recommended if frequency criteria are not met 2, 9