EENT · PANCE / PANRE

Group A Streptococcal Pharyngitis

GAS bacterial pharyngitis — diagnose with RADT/culture and treat with penicillin to prevent rheumatic fever.

Also known as: GAS pharyngitis, strep throat, group A strep, streptococcal pharyngitis

Overview

Acute pharyngitis caused by Streptococcus pyogenes (group A beta-hemolytic Streptococcus, GAS). Distinguished from far more common viral pharyngitis by clinical features supported by rapid antigen detection test (RADT) and/or throat culture.

Epidemiology

GAS causes 15-30% of pharyngitis in children and 5-15% in adults. Most common in children 5-15 years. Peak in late winter/early spring. Spread by respiratory droplets; incubation 2-5 days. Asymptomatic carriage 5-20% in school-age children.

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Risk factors

School-age children (5-15 years)
Close contact with infected individual
Late winter / early spring
Crowded living conditions (schools, military barracks)
Caregiver/parent of school-age child

Pathophysiology

S. pyogenes (Lancefield group A) adheres to pharyngeal epithelium via M protein, lipoteichoic acid, and fibronectin-binding proteins. Streptolysins and pyrogenic exotoxins cause local inflammation and systemic symptoms. Suppurative complications (peritonsillar abscess, otitis) arise from contiguous spread. Nonsuppurative sequelae (acute rheumatic fever, post-streptococcal glomerulonephritis) reflect immune-mediated cross-reactivity.

Clinical presentation

Symptoms

Sudden onset sore throat, painful swallowing
Fever ≥38°C (100.4°F)
Headache, malaise
Nausea, vomiting, abdominal pain (especially children)
ABSENCE of cough, rhinorrhea, conjunctivitis, hoarseness — strongly suggests GAS over viral

Signs / physical exam

Tonsillopharyngeal erythema with exudates
Tender anterior cervical lymphadenopathy
Palatal petechiae (uvular or soft palate)
Scarlatiniform rash (sandpaper-like), strawberry tongue, circumoral pallor → scarlet fever
Absence of viral features

Classic findings

Modified Centor (McIsaac) score components: fever >38, tonsillar exudate, tender anterior cervical adenopathy, absence of cough, age 3-14 (+1) or 15-44 (0) or ≥45 (-1).

Differential diagnosis

Viral pharyngitis (adenovirus, rhinovirus, coronavirus) — Cough, rhinorrhea, conjunctivitis, hoarseness, viral exanthem — argue AGAINST GAS; supportive care
Infectious mononucleosis (EBV) — Adolescent/young adult with fatigue, posterior cervical lymphadenopathy, palatal petechiae, splenomegaly, atypical lymphocytes; heterophile (Monospot) or EBV serology; rash develops in ~90% if amoxicillin given
Acute HIV (seroconversion) — Sore throat, fever, lymphadenopathy, mucocutaneous ulcers, rash; HIV RNA or 4th-gen antibody/antigen test
Gonococcal pharyngitis — Often asymptomatic; risk factors (oral sex, MSM); NAAT
Peritonsillar abscess — Trismus, deviated uvula, hot-potato voice; needs drainage
Retropharyngeal abscess — Neck stiffness, drooling, stridor; lateral neck XR or CT
Epiglottitis — Drooling, tripoding, muffled voice, severe sore throat with minimal pharyngeal findings; thumbprint sign on lateral neck XR
Diphtheria — Gray adherent pseudomembrane, unvaccinated; toxin neutralization required
Lemierre syndrome — Persistent fever after pharyngitis, unilateral neck pain/swelling, internal jugular vein thrombophlebitis with septic pulmonary emboli; usually Fusobacterium necrophorum
Kawasaki disease (children <5) — ≥5 days fever + 4 of 5 criteria (conjunctivitis, mucositis, rash, extremity changes, cervical lymphadenopathy); echo for coronary aneurysms

Diagnostic workup

Diagnostic criteria

IDSA 2012: confirm GAS pharyngitis with positive RADT or throat culture in symptomatic patients with clinical features suggestive of GAS (Centor ≥2-3); do not test those with overt viral features. Test of cure NOT routine.

Labs

Rapid antigen detection test (RADT) — sensitivity ~85%, specificity >95%
Throat culture (gold standard, ~90-95% sensitive) — required to confirm negative RADT in children/adolescents per IDSA; not necessary in adults given low GAS prevalence and minimal rheumatic fever risk
Do NOT test asymptomatic patients (high carriage rate, false positives)
Do NOT test patients with clear viral features (cough, coryza, conjunctivitis, hoarseness)
ASO and anti-DNase B titers — for documenting prior GAS infection in rheumatic fever evaluation, not acute diagnosis
Heterophile (Monospot) or EBV-specific serology if mononucleosis suspected

Imaging

Not required for uncomplicated GAS pharyngitis
Lateral neck XR or CT if epiglottitis, retropharyngeal abscess, or deep neck infection suspected

Diagnostic algorithm

Modified Centor Criterion	Points
Fever >38°C (100.4°F)	+1
Absence of cough	+1
Tender anterior cervical lymphadenopathy	+1
Tonsillar exudate or swelling	+1
Age 3-14 years	+1
Age 15-44 years	0
Age ≥45 years	-1
Score 0-1: no testing, no antibiotic	—
Score 2-3: RADT; treat if positive	—
Score 4-5: RADT (some empiric treatment); culture if RADT negative in children	—

Modified Centor (McIsaac) score for risk stratification of GAS pharyngitis.

Treatment

First-line

Penicillin V 500 mg PO BID-TID × 10 days (adults) OR amoxicillin 50 mg/kg/day (max 1000 mg) once daily × 10 days (children) — narrow-spectrum, low cost, no documented resistance
Penicillin G benzathine 1.2 million units IM × 1 (adults; 600,000 units if <27 kg) — single-dose option, ensures adherence
Supportive care: acetaminophen or NSAIDs, saltwater gargles, hydration
Treatment within 9 days of symptom onset prevents acute rheumatic fever; symptomatic improvement within 24-48 h
Return to school/work after 12-24 h of antibiotic therapy and afebrile

Second-line / adjunct

Penicillin allergy (non-anaphylactic): cephalexin 500 mg BID × 10 days, cefadroxil, or cefuroxime
Severe penicillin allergy: azithromycin × 5 days OR clindamycin × 10 days (check local macrolide resistance; rising in US ~5-15%)
Recurrent symptomatic GAS: confirm true infection (not carrier with intercurrent viral illness); consider clindamycin or amox-clav for re-treatment
Tonsillectomy considered for ≥7 episodes/year, ≥5/year × 2 years, or ≥3/year × 3 years (Paradise criteria) plus documentation in each

Complications

Suppurative: peritonsillar abscess, otitis media, sinusitis, retropharyngeal abscess, cervical lymphadenitis, Lemierre syndrome
Nonsuppurative — acute rheumatic fever (peaks 2-4 weeks after pharyngitis; PREVENTABLE by antibiotic treatment within 9 days)
Nonsuppurative — post-streptococcal glomerulonephritis (1-2 weeks after; NOT prevented by antibiotics; hematuria, edema, hypertension, low complement)
Scarlet fever (erythrogenic toxin)
Toxic shock syndrome and necrotizing fasciitis (rare, severe invasive disease)
PANDAS — pediatric autoimmune neuropsychiatric disorder (controversial)

PANCE pearls

Cough, coryza, conjunctivitis, hoarseness, oral ulcers → VIRAL. Do not test or treat for strep.
Centor/McIsaac score guides testing: ≥3 → RADT; <3 → no test, no antibiotic.
Amoxicillin given to mono produces a non-IgE-mediated maculopapular rash in 80-90% of patients — not a true penicillin allergy.
Antibiotics prevent acute rheumatic fever but NOT post-streptococcal glomerulonephritis.
No documented GAS resistance to penicillin — penicillin remains first-line; macrolide resistance rising.
Test-of-cure not recommended unless symptomatic recurrence or prior rheumatic fever.

References

IDSA 2012 — Shulman ST et al. Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis (Update). Clin Infect Dis 2012;55(10):e86-e102
AAP Red Book 2024 — American Academy of Pediatrics. Group A Streptococcal Infections. In: Red Book 2024
AHA — Gerber MA et al. Prevention of Rheumatic Fever and Diagnosis and Treatment of Acute Streptococcal Pharyngitis. Circulation 2009;119(11):1541-1551

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