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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Most acute pharyngitis is viral; cough, rhinorrhea, hoarseness, oral ulcers, or conjunctivitis argue against GAS testing
- GAS clues: fever, tonsillar exudates, tender anterior cervical nodes, absence of cough, age 5-15 years
- Do not treat empirically in most cases; confirm with rapid antigen detection test or throat culture when GAS is plausible
- Children/adolescents with negative RADT need backup throat culture; adults usually do not
- First-line GAS treatment: penicillin V or amoxicillin for 10 days; treatment prevents acute rheumatic fever
Overview
Acute pharyngitis is inflammation of the pharynx and tonsils. Viruses cause most cases, including rhinovirus, coronavirus, adenovirus, influenza, EBV, and others. Group A Streptococcus is the key bacterial cause because treatment prevents acute rheumatic fever, reduces suppurative complications, and decreases transmission. Clinical scoring such as Centor or McIsaac helps decide who should be tested, but symptoms alone are not reliable enough to confirm GAS.
Epidemiology
GAS pharyngitis is most common in school-aged children and adolescents, especially ages 5-15, and is uncommon under age 3 unless there is close exposure. Adults have lower GAS prevalence. Transmission occurs by respiratory droplets. Acute rheumatic fever is now uncommon in the United States but remains the central reason for accurate diagnosis and adequate treatment. EBV infectious mononucleosis should be considered in adolescents or young adults with profound fatigue, posterior cervical lymphadenopathy, hepatosplenomegaly, or atypical lymphocytosis.
Clinical Features
Symptoms
Sore throat and odynophagia
Fever and abrupt onset support GAS but are not diagnostic
Cough, rhinorrhea, hoarseness, oral ulcers, or conjunctivitis suggest viral cause
Fatigue, posterior cervical lymphadenopathy, palatal petechiae, or splenomegaly suggests EBV
Trismus, muffled voice, uvular deviation, or drooling suggests peritonsillar abscess
Neck swelling, stridor, tripod positioning, or toxic appearance suggests deep neck infection or epiglottitis
Signs
Tonsillar erythema or exudates
Tender anterior cervical lymphadenopathy supports GAS
Palatal petechiae may occur with GAS or EBV
Posterior cervical nodes and hepatosplenomegaly favor EBV
Scarlatiniform sandpaper rash suggests scarlet fever
Unilateral tonsillar bulge with uvular deviation suggests peritonsillar abscess
Investigations
First-line
Centor/McIsaac clinical assessmentFever, tonsillar exudate, tender anterior cervical nodes, absence of cough, and age adjustment guide testing decisions
Rapid antigen detection test (RADT)Use when GAS is plausible and viral features are absent. Positive RADT confirms GAS and permits treatment
Second-line
Throat cultureBackup culture after negative RADT in children/adolescents; also useful during outbreaks or when high suspicion persists
EBV testingHeterophile antibody or EBV serology if mononucleosis suspected; CBC may show atypical lymphocytes
NAAT for GASHighly sensitive molecular testing may replace culture depending on setting
Specialist
ImagingNot needed for routine pharyngitis; CT neck with contrast if deep neck abscess suspected
HIV, gonorrhea, diphtheria testingConsider based on sexual exposure, travel/vaccination status, pseudomembrane, or systemic features
1
When not to test or treat for GAS
- Do not test patients with clear viral features such as cough, rhinorrhea, hoarseness, oral ulcers, or conjunctivitis
- Do not test asymptomatic household contacts routinely
- Do not use antibiotics for viral pharyngitis
2
Confirmed GAS treatment
- Penicillin V for 10 days or amoxicillin for 10 days are first-line
- Single-dose IM benzathine penicillin G if adherence is uncertain
- Non-anaphylactic penicillin allergy: cephalexin or cefadroxil
- Anaphylactic beta-lactam allergy: clindamycin, azithromycin, or clarithromycin, considering local resistance
3
Supportive care
- NSAIDs or acetaminophen, hydration, salt-water gargles, and rest
- Avoid aspirin in children due to Reye syndrome risk
- Corticosteroids are not routinely recommended for uncomplicated GAS pharyngitis
4
Complications and recurrence
- Patients are generally noninfectious after 12-24 h of appropriate antibiotics and clinical improvement
- Recurrent positive tests may represent carrier state plus viral infections; avoid repeated antibiotics unless high-risk features
- Evaluate for peritonsillar abscess if unilateral worsening pain, trismus, or muffled voice develops
Complications
- Peritonsillar abscess: Unilateral sore throat, trismus, uvular deviation
- Acute rheumatic fever: Migratory polyarthritis, carditis, chorea, erythema marginatum, subcutaneous nodules after GAS
- Post-streptococcal glomerulonephritis: Hematuria, edema, hypertension; antibiotics do not reliably prevent it
- Scarlet fever: Sandpaper rash and strawberry tongue
- EBV splenic rupture: Avoid contact sports when splenomegaly/mononucleosis is present
USMLE Step 2 CK Exam Tips
- 1Cough + rhinorrhea + hoarseness = viral pharyngitis; no GAS testing needed
- 2GAS testing is appropriate when Centor/McIsaac features are present and viral features are absent
- 3Negative rapid strep in a child needs backup culture; in adults it usually does not
- 4First-line treatment for confirmed GAS is penicillin or amoxicillin for 10 days
- 5Ampicillin/amoxicillin rash in EBV is not a true penicillin allergy
- 6Posterior cervical LAD + splenomegaly + fatigue = EBV; avoid contact sports
- 7Treating GAS prevents acute rheumatic fever but does not reliably prevent post-strep glomerulonephritis
- 8Trismus and uvular deviation are not simple pharyngitis — think peritonsillar abscess
practicetest your knowledge on acute pharyngitis (gas vs viral)Apply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — ent and beyond.
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