What is the diagnosis and treatment for a child presenting with a rash, fever, and sore throat, consistent with a picture of scarlet fever?

Scarlet Fever: Diagnosis and Treatment

Clinical Diagnosis

A child presenting with fever, sore throat, and rash consistent with scarlet fever should receive immediate antibiotic treatment with Penicillin V 250-500 mg every 6-8 hours for 10 days after confirming Group A Streptococcus (GAS) infection with rapid antigen detection test (RADT) or throat culture. 1, 2, 3

Key Diagnostic Features

The classic presentation includes:

• Sudden onset sore throat with pain on swallowing, typically in children aged 5-15 years 1, 4
• Fever ≥38°C (102°F), though absence of fever does not exclude diagnosis 2, 4
• Characteristic sandpaper-like rash beginning on trunk and spreading to extremities, with accentuation in the perineal region 2, 4, 5
• "Strawberry tongue" - initially white-coated, then bright red with prominent papillae 4, 6
• Tonsillopharyngeal erythema with or without exudates 1, 4
• Palatal petechiae 1, 4
• Tender anterior cervical lymphadenopathy 1

Laboratory Confirmation Required

Do not rely on clinical features alone - even experienced clinicians cannot reliably differentiate bacterial from viral pharyngitis without testing. 1, 7

Testing algorithm:

1. Perform RADT first on throat swab from posterior pharynx and tonsillar surfaces 2, 7
2. If RADT positive → diagnostic for GAS, start antibiotics immediately 1, 2
3. If RADT negative in children/adolescents → obtain backup throat culture (gold standard) 1, 2
4. In adults with negative RADT, backup culture generally not necessary due to low rheumatic fever risk 1

Do NOT test if viral features predominate: conjunctivitis, coryza, cough, hoarseness, discrete oral ulcers, or diarrhea 1, 2

Treatment Recommendations

First-Line Antibiotic Therapy

Penicillin V (phenoxymethylpenicillin) remains the gold standard due to proven efficacy, narrow spectrum, safety, low cost, and zero resistance. 2, 7, 3

Dosing for streptococcal infections including scarlet fever:

• Children and adults: 250-500 mg (400,000-800,000 units) every 6-8 hours for 10 days 2, 3
• Alternative dosing: 500 mg twice daily or 250 mg three times daily 2
• Critical: Complete the full 10-day course to prevent rheumatic fever and ensure bacterial eradication 2, 7

Penicillin Allergy Alternatives

For non-anaphylactic penicillin allergy:

• First-generation cephalosporins (cephalexin or cefadroxil) for 10 days 1, 7

For true penicillin allergy or anaphylactic history:

• Clindamycin - excellent option with only ~1% GAS resistance in the U.S. 7
• Macrolides (azithromycin, clarithromycin, erythromycin) - use with caution due to 5-8% resistance rates 1, 7

Avoid: Sulfonamides (associated with increased disease severity and mortality), fluoroquinolones, and tetracyclines 2, 7

Critical Timing Considerations

• Antibiotics can be started up to 9 days after symptom onset and still prevent rheumatic fever 2, 4
• Patient becomes non-contagious after 24 hours of antibiotic therapy 2, 7
• Early treatment reduces infectivity period and morbidity 2

Symptomatic Management

• Antipyretics: Acetaminophen or NSAIDs for fever and pain relief 1, 2
• Never use aspirin in children under 16 years due to Reye's syndrome risk 2, 7
• Antipyretics provide symptomatic relief but do not replace antibiotics 2

Complications if Untreated

Early antibiotic treatment is essential to prevent serious sequelae:

• Suppurative complications: Peritonsillar abscess, cervical lymphadenitis 2
• Non-suppurative complications: Acute rheumatic fever, acute glomerulonephritis, endocarditis 2, 5, 6
• Systemic complications: Bacteremia, pneumonia, meningitis 5

Infection Control

• Isolate patient for minimum 24 hours after starting effective antibiotic therapy 2
• Healthcare workers must use disposable gloves and aprons with strict hand hygiene 2
• Routine throat cultures or treatment for asymptomatic household contacts generally not necessary unless outbreak situation 2

Follow-Up and Monitoring

• Monitor for 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 not routinely recommended unless symptoms persist or recur 2

Common Pitfalls to Avoid

• Do not delay treatment waiting for "classic" presentation - the complete clinical picture varies, and early treatment prevents complications 4
• Do not treat based on clinical impression alone - microbiological confirmation prevents antibiotic overuse 7
• Recognize GAS carriers - asymptomatic carriers may have positive cultures during viral pharyngitis episodes; look for viral features and lack of sudden onset 2, 7
• Do not use broad-spectrum antibiotics when narrow-spectrum options available - promotes resistance and increases cost 7