What are the clinical presentation and treatment of scarlet fever?

Scarlet Fever: Clinical Presentation and Treatment

Clinical Presentation

Scarlet fever presents with a distinctive triad of sore throat (often severe with pain on swallowing), high fever (typically ≥38°C/102°F), and a characteristic sandpaper-like rash, most commonly affecting children aged 5-15 years. 1, 2, 3

Cardinal Features

Pharyngeal Findings:

• Severe tonsillopharyngeal erythema with or without exudates 1
• Palatal petechiae (distinguishes from viral pharyngitis) 1
• "Strawberry tongue" - initially white-coated, then bright red with prominent fungiform papillae 1, 4

Characteristic Rash:

• Appears as blanching, erythematous, maculopapular eruption with sandpaper-like texture 3, 5
• Typically begins on trunk and spreads to extremities 3
• Accentuation in perineal region with early desquamation possible 6, 1
• Usually spares the face 3
• Desquamation occurs 1-2 weeks after onset, particularly affecting fingers and toes 6

Systemic Features:

• High fever persisting for at least 5 days if untreated 2
• Cervical lymphadenopathy (usually unilateral) 2
• Headache, malaise, and occasionally nausea/vomiting 5

Key Distinguishing Features

Unlike viral pharyngitis: Scarlet fever rarely presents with cough, hoarseness, or conjunctivitis 1, 7

Unlike Kawasaki disease: Scarlet fever has exudative pharyngitis and responds rapidly to antibiotics within 24-48 hours 1, 2

Unlike Rocky Mountain Spotted Fever: Scarlet fever rash appears earlier in illness, rarely becomes petechial, and does not typically involve palms/soles initially 6, 1

Diagnostic Approach

Obtain throat culture or rapid antigen detection test (RADT) to confirm Group A Streptococcus before initiating antibiotics. 2

• Swab the posterior pharynx and tonsillar surfaces bilaterally 2
• Throat culture remains the reference standard for confirming GAS pharyngitis 2
• Do not delay treatment if clinical suspicion is high and patient has typical features 3, 5

Treatment

Initiate oral Penicillin V (phenoxymethylpenicillin) 250-500 mg every 6-8 hours for 10 days immediately upon diagnosis. 2, 8

Antibiotic Regimens

First-line therapy:

• Penicillin V 250-500 mg orally every 6-8 hours for 10 days 2, 8
• Alternative dosing: 500 mg twice daily or 250 mg three times daily 2

For penicillin allergy:

• First-generation cephalosporins (if no immediate hypersensitivity to β-lactams) 2
• Macrolides (erythromycin) for true penicillin allergy, though be aware of potential macrolide resistance 2, 9

Critical timing considerations:

• Antibiotics can be started up to 9 days after symptom onset and still prevent rheumatic fever 2
• Patient becomes non-contagious after 24 hours of antibiotic therapy 2
• Early treatment reduces infectivity period and morbidity 2

Important Caveats

Never use sulfonamide antibiotics - they are associated with increased disease severity and mortality in streptococcal infections 2

Never use aspirin for fever control in children under 16 years due to risk of Reye's syndrome 2

Monitoring and Follow-up

• Expect clinical improvement within 48-72 hours of starting antibiotics 2
• If symptoms persist beyond 3-5 days of antibiotic therapy, reassess diagnosis and consider alternative pathogens 2
• Post-treatment throat cultures are not routinely recommended unless symptoms persist or recur 2
• Routine throat cultures or treatment for asymptomatic household contacts is generally not necessary 2

Complications if Untreated

Early recognition and treatment are essential to prevent serious sequelae including:

• Acute rheumatic fever 5, 4
• Post-streptococcal glomerulonephritis 5, 4
• Bacteremia and sepsis 5
• Pneumonia 5
• Endocarditis 5, 4
• Meningitis 5