What is the appropriate diagnosis and treatment for a pediatric patient presenting with a sandpapery rash, fever, sore throat, reduced oral intake, and a wet cough, suspected to have scarlet fever?

Scarlet Fever: Diagnosis and Treatment

Immediate Diagnostic Approach

For a pediatric patient presenting with sandpaper rash, fever, sore throat, reduced oral intake, and wet cough, obtain a rapid antigen detection test (RADT) or throat culture immediately to confirm Group A Streptococcus (GAS) infection before initiating antibiotics. 1, 2

Key Clinical Features to Confirm

• Characteristic sandpaper-like papular rash with possible accentuation in the perineal region 1, 2
• "Strawberry tongue" (initially white-coated, then bright red with prominent papillae) - pathognomonic for scarlet fever 3, 2
• Tonsillopharyngeal erythema with or without exudates 3, 2
• Palatal petechiae and beefy red swollen uvula 2
• Tender enlarged anterior cervical lymph nodes 2
• Severe sore throat with pain on swallowing 3

Important Caveat About the Wet Cough

The presence of wet cough is atypical for scarlet fever and suggests a concurrent viral infection or alternative diagnosis. 4, 1 Scarlet fever rarely presents with cough, hoarseness, or conjunctivitis 3. When viral features like cough predominate, testing for GAS may not be indicated unless other classic features strongly suggest bacterial infection 1.

Diagnostic Testing Algorithm

1. Perform RADT first as the initial diagnostic test 1
2. If RADT is negative in children/adolescents, obtain backup throat culture (gold standard) 1, 2
3. Proper specimen collection: Swab the posterior pharynx and tonsillar surfaces bilaterally 1
4. Do not rely on clinical features alone - microbiological confirmation is mandatory before starting antibiotics 2

When NOT to Test

• If viral features predominate: conjunctivitis, coryza, cough, hoarseness, discrete ulcerative stomatitis, viral exanthem, or diarrhea 1
• Children under 3 years old unless specific risk factors present (e.g., older sibling with GAS infection) 4, 1

Treatment Recommendations

Once GAS is confirmed, initiate oral Penicillin V 250 mg three times daily (or 250 mg twice daily for younger children) for 10 days. 4, 1

First-Line Antibiotic Options

• Penicillin V (oral):

  • Children: 250 mg twice or three times daily
  • Adolescents/adults: 250 mg four times daily or 500 mg twice daily
  • Duration: 10 days 4

• Amoxicillin (oral):

  • 50 mg/kg once daily (max 1000 mg) OR 25 mg/kg twice daily (max 500 mg/dose)
  • Duration: 10 days 4

• Benzathine penicillin G (intramuscular):

  • <27 kg: 600,000 units
  • ≥27 kg: 1,200,000 units
  • Single dose 4

For Penicillin-Allergic Patients

• First-generation cephalosporins (if no immediate hypersensitivity):

  • Cephalexin: 20 mg/kg/dose twice daily (max 500 mg/dose) for 10 days 4
  • Cefadroxil: 30 mg/kg once daily (max 1 g) for 10 days 4

• For true penicillin allergy:

  • Clindamycin: 7 mg/kg/dose three times daily (max 300 mg/dose) for 10 days 4
  • Azithromycin: 12 mg/kg once daily (max 500 mg) for 5 days 4
  • Clarithromycin: 7.5 mg/kg/dose twice daily (max 250 mg/dose) for 10 days 4

Important: Macrolide resistance varies geographically and temporally 4, 1. Never use sulfonamide antibiotics - they are associated with increased disease severity and mortality 1.

Critical Treatment Principles

• Antibiotics can be started up to 9 days after symptom onset and still prevent rheumatic fever 1
• Patient becomes non-contagious after 24 hours of antibiotic therapy 1
• Complete the full 10-day course - shorter durations lack evidence for preventing complications 1
• Early treatment reduces infectivity period and morbidity 1

Adjunctive Symptomatic Management

• Use acetaminophen or ibuprofen for fever and pain relief 4, 1
• Never use aspirin in children due to risk of Reye's syndrome 4, 1
• Corticosteroids are not recommended 4

Monitoring and Follow-Up

• Expect clinical improvement within 48-72 hours of starting antibiotics 1
• If symptoms persist beyond 3-5 days of antibiotic therapy, reassess the diagnosis and consider alternative pathogens 1
• Post-treatment throat cultures are not routinely recommended unless symptoms persist or recur 4, 1
• Do not test or treat asymptomatic household contacts routinely 4, 1

Critical Complications if Untreated

Early antibiotic treatment is essential to prevent serious sequelae, including:

• Suppurative complications: peritonsillar abscess 1
• Non-suppurative complications: acute rheumatic fever, acute glomerulonephritis, endocarditis 1, 5, 6

Common Pitfalls to Avoid

• Do not diagnose based on clinical features alone - always confirm with RADT or culture 2
• Beware of asymptomatic GAS carriers with concurrent viral pharyngitis - the presence of viral features (cough, coryza) and lack of sudden onset suggest carrier state rather than acute infection 1
• Do not use co-amoxiclav as first-line - it has broader spectrum, higher GI side effects, and increased resistance risk 1
• In this specific case, the wet cough warrants careful consideration - if viral features predominate, the patient may be a GAS carrier with viral pharyngitis rather than true scarlet fever 1