Acute pharyngitis

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Acute Pharyngitis

Definition

Acute pharyngitis is inflammation of the pharynx presenting as sore throat, typically lasting days. Sore throat is not synonymous with pharyngitis - it can also arise from peritonsillar/retropharyngeal abscesses, thyroiditis, GERD, tumors, and postnasal drainage.

Harrison's Principles of Internal Medicine 22E, p. 1709

Etiology

Viral (Most Common)

Virus	Clinical Notes
Rhinovirus	Most common cause of the common cold
Coronavirus	Common cold
Parainfluenza	Common cold, croup
Influenza A & B	Widespread outbreaks; sore throat may be the chief complaint, but myalgia, headache, and fatigue predominate
Adenovirus	Pharyngoconjunctival fever (pharyngitis + conjunctivitis)
Coxsackie A	Herpangina (vesicular eruption on soft palate/anterior pillar with fever); hand-foot-mouth disease
Epstein-Barr virus (EBV)	Infectious mononucleosis - prominent exudate mimicking strep; marked posterior cervical adenopathy, splenomegaly, palatine petechiae
Cytomegalovirus (CMV)	CMV mononucleosis (milder pharyngitis than EBV)
Herpes simplex 1 & 2	Pharyngitis, gingivostomatitis; vesicles and shallow ulcers on palate; mainly in adolescents
HIV	Acute retroviral syndrome - fever, rash, lymphadenopathy, weight loss + sore throat

Bacterial

Organism	Clinical Notes
Group A beta-hemolytic Streptococcus (GABHS / S. pyogenes)	Most important bacterial cause - pharyngitis, tonsillitis, scarlet fever; 15-30% of pediatric sore throats, 5-15% in adults
Groups B, C, G streptococci	Clinically indistinguishable from GAS; C and G can cause acute glomerulonephritis but NOT rheumatic fever
Arcanobacterium (Arcobacterium) haemolyticum	Mainly adolescents and young adults; scarlatiniform rash on extensor surfaces (doesn't peel); resistant to penicillin - use erythromycin
Neisseria gonorrhoeae	Sexually active adolescents; fellatio is high-risk; may be exudative; treat with IM ceftriaxone + azithromycin (for chlamydia co-infection)
Corynebacterium diphtheriae	Grayish adherent pseudomembrane, slow onset, marked systemic toxicity; rare in vaccinated populations
Mixed anaerobes (Fusobacterium spp., spirochetes)	Vincent's angina (anaerobic pharyngitis) - foul breath, purulent exudate
Mycoplasma pneumoniae	Pharyngitis with bronchopulmonary symptoms
Chlamydia pneumoniae	Pharyngitis, pneumonia
Yersinia enterocolitica	Exudative pharyngitis + cervical lymphadenopathy + abdominal pain/diarrhea; high mortality
Treponema pallidum	Secondary syphilis - oval red maculopapules/patches on pharynx
Francisella tularensis	Typhoidal/oropharyngeal tularemia

Fungal

Candida spp. - appears as cottage cheese-like plaques that scrape off and leave a bleeding surface; distinguish from exudate of pharyngitis
KJ Lee's Essential Otolaryngology, p. 685
Cummings Otolaryngology Head and Neck Surgery, p. 1142
Textbook of Family Medicine 9e, p. 268

Clinical Features and Differential Diagnosis

Clinical findings suggesting specific diagnoses (Harrison's Table 37-3):

Finding	Suspected Diagnosis
Scarlatiniform rash	GABHS or A. haemolyticum
Cough + otitis media	H. influenzae
Fellatio history; sore throat unresponsive to penicillin	N. gonorrhoeae
Travel to endemic area + pseudomembrane	C. diphtheriae
Persistent sore throat + bronchopulmonary symptoms	M. pneumoniae
Posterior cervical/auricular adenopathy, splenomegaly, palatine petechiae, gelatinous uvula	Acute infectious mononucleosis
New sexual partner in prior month, fever, rash, myalgias	Acute HIV infection
Kawasaki disease clues: conjunctivitis, erythematous lips, strawberry tongue, rash, edema of hands/feet	Kawasaki disease (coronary artery involvement possible)

Diagnosing Group A Strep (GAS) vs. Viral Pharyngitis

Centor Criteria (Adults)

Assign 1 point each for:

Fever (history)
Tonsillar exudates
Tender anterior cervical lymphadenopathy
Absence of cough

McIsaac modification adds -1 point for age ≥45.

Score	Action
0-1	No testing or antibiotics needed
2-3	Rapid antigen detection test (RADT)
4	RADT or empirical antibiotic treatment

In children, the Centor criteria are less specific - testing should be performed when signs of pharyngitis are present without signs of viral infection (conjunctivitis, runny nose, cough, hoarseness, nonexudative oral lesions).

Diagnostic Tests

Rapid Antigen Detection Test (RADT): Sensitivity ~80%, specificity ~95%; results in minutes; preferred in adults
Throat culture: Sensitivity ~85-90% (single swab); gold standard but 24-48h delay; recommended in children when RADT is negative
Note: Neither test differentiates true infection from GAS carriage (carriage rate up to 20% in schoolchildren)
Harrison's Principles of Internal Medicine 22E, p. 1748-1752
Textbook of Family Medicine 9e, p. 268

Medical Emergencies in the Differential (Must Exclude)

These five dangerous syndromes can mimic acute pharyngitis and must not be missed:

Acute epiglottitis (supraglottitis): Life-threatening; sudden fever, dysphagia, dysphonia, drooling, tripod position; 80% mortality with airway obstruction - secure airway before any diagnostic attempt
Peritonsillar abscess (quinsy): Medial tonsil displacement, "hot potato" voice, trismus (in ~2/3 of cases), ipsilateral ear pain, drooling
Ludwig's angina (submandibular space infection): Woody induration of submandibular area, stiff neck, drooling, dysphagia
Retropharyngeal space infection: Bulge in posterior pharyngeal wall; mixed aerobic/anaerobic bacteria
Lemierre syndrome (septic thrombosis of internal jugular vein): Fusobacterium spp.; fever, septic pulmonary emboli, pleural effusions

Textbook of Family Medicine 9e, p. 268

Treatment

Symptomatic (All Pharyngitis)

Analgesics: acetaminophen or NSAIDs
Saline gargles, humidification, soft foods, tea with honey

GAS - Antibiotic Therapy

Why treat? - Prevent acute rheumatic fever (still relevant in developing countries), reduce duration and severity, prevent suppurative complications, reduce transmission. Treatment prevents ARF even if started up to 9 days after symptom onset.

First-line:

Penicillin V (oral, 10 days) or amoxicillin (suspension preferred in children) - narrow spectrum, low cost, safe
Benzathine penicillin G IM - single injection, ensures compliance

Penicillin allergy:

First-generation cephalosporin (if non-anaphylactic allergy)
Azithromycin or other macrolide (note: macrolide resistance in GAS is rising in some regions)
Clindamycin (alternative)

Do NOT use: Fluoroquinolones, tetracyclines, or chloramphenicol for GAS

Harrison's Principles of Internal Medicine 22E, p. 1767
Textbook of Family Medicine 9e, p. 268
Red Book 2021, p. 2975

Complications of Streptococcal Pharyngitis

Suppurative

Peritonsillar abscess
Sinusitis
Otitis media
Mastoiditis
Retropharyngeal abscess

Non-suppurative (Immune-mediated)

Acute Rheumatic Fever (ARF): Prevented by timely antibiotic therapy
Acute Post-Streptococcal Glomerulonephritis (APSGN): NOT prevented by antibiotics
Scarlet fever (from erythrogenic toxin-producing strains)

Groups C and G streptococci can cause acute glomerulonephritis but have never been shown to cause acute rheumatic fever.

Special Considerations

Asymptomatic GAS carriers: Do not need treatment in most situations; difficult to distinguish from true infection on culture alone
High-risk patients (lower threshold to treat): History of ARF, documented GAS exposure, community epidemic, diabetes, immunocompromised
Infectious mononucleosis: Avoid amoxicillin/ampicillin (causes diffuse maculopapular rash in ~80%); avoid contact sports (splenomegaly/rupture risk)
Primary HIV infection: Consider in patients with sore throat + fever, rash, myalgias, lymphadenopathy, new sexual partner

Sources: Harrison's Principles of Internal Medicine 22E (2025) | KJ Lee's Essential Otolaryngology | Textbook of Family Medicine 9e | Cummings Otolaryngology Head and Neck Surgery | Red Book 2021

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