Streptococcal Pharyngitis
System: HEENT Infections · Parent MOC: MOC - Diseases by System
One-Sentence Definition
Acute pharyngitis caused by Streptococcus pyogenes (GAS), important mainly to treat symptoms, limit transmission, and prevent acute rheumatic fever in at-risk populations.
Clinical Presentation
- Sudden sore throat, fever, tender anterior cervical nodes, tonsillar exudate; scarlatiniform rash in scarlet fever
- Usually no cough/rhinorrhea (those favor viral)
- Centor / McIsaac scores triage testing
Pathogens
| Organism | Notes |
|---|---|
| Streptococcus pyogenes | Lancefield group A |
| Viral (majority of pharyngitis) | EBV, adeno, etc. — MOC - Virology |
| Fusobacterium (Lemierre — rare) | Adolescent septic jugular thrombophlebitis |
Pathogenesis
- Local invasion + streptococcal pyrogenic exotoxins (scarlet fever)
- Post-infectious: acute rheumatic fever, PSGN — MOC - Immunology
Diagnosis
| Step | Test | Note |
|---|---|---|
| RADT | Rapid antigen | Confirm negatives with culture in children per local practice |
| Throat culture | Gold for GAS | |
| Avoid | Testing viral-looking illness indiscriminately | Stewardship |
Treatment Principles
- Penicillin / amoxicillin drug of choice (GAS remains susceptible)
- Macrolides only if true penicillin allergy — watch resistance
- Symptom care; school return rules after 12–24h antibiotics
Prevention
- Treat proven GAS to reduce ARF risk where relevant
- Household hygiene; outbreak management in institutions
Differential / Pitfalls
- Viral pharyngitis, mono (EBV — rash if ampicillin), peritonsillar abscess, epiglottitis (different age/look)
- Treating everyone with sore throat → resistance + CDI risk (Clostridioides difficile Infection)
Learning Aids
Clinical Example
Example
Case: 8yo, fever, exudative tonsils, tender nodes, no cough; RADT positive.
Question: Drug of choice and one nonsuppurative complication you prevent?
Answer: Penicillin/amoxicillin for Streptococcus pyogenes. Prevents acute rheumatic fever (PSGN not clearly prevented by abx the same way — know the teaching nuance).
Related
- HEENT Infections · Streptococcus pyogenes
- Cellulitis and Skin Abscess (invasive GAS spectrum)
- MOC - Immunology
Active Recall
- Clinical features favoring GAS over viral?
- Why penicillin still first-line?
- Name two post-streptococcal diseases.