What is the treatment for a patient presenting with a strep rash, indicative of scarlet fever or another streptococcal infection?

Strep Rash: Signs, Symptoms, and Treatment

Clinical Presentation of Scarlet Fever (Strep Rash)

The classic strep rash, known as scarlet fever, presents with a distinctive sandpaper-like erythematous rash that typically begins on the trunk and spreads to the extremities, with accentuation in skin folds (particularly the perineal region), accompanied by fever ≥38°C (102°F), sore throat, and characteristic oral changes. 1

Key Diagnostic Features

• Rash characteristics: Fine, red, blanching papules giving a "sandpaper" texture to the skin, with early desquamation possible in flexural areas 1
• Oral findings: "Strawberry tongue" (initially white-coated, then red and bumpy), pharyngeal erythema, and tonsillar exudate 1
• Systemic symptoms: Sudden-onset sore throat with severe pain on swallowing, fever typically 101-104°F, headache, and nausea/vomiting, especially in children aged 5-15 years 1
• Lymphadenopathy: Cervical lymph nodes, usually unilateral and tender 1

Distinguishing from Viral Illness

• Absence of viral features strongly suggests bacterial etiology: no coryza, hoarseness, cough, conjunctivitis, or discrete ulcerative stomatitis 1
• The rash appears earlier in scarlet fever compared to viral exanthems and rarely becomes petechial 1
• Viral pharyngitis generally lacks the sudden onset, high fever, and severe throat pain characteristic of Group A Streptococcus 1

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Immediate Diagnostic Approach

Confirm Group A Streptococcus infection with rapid antigen detection test (RADT) or throat culture before initiating antibiotics, as clinical features alone cannot reliably distinguish bacterial from viral pharyngitis. 1

Testing Algorithm

• First-line: Perform RADT on throat swab from posterior pharynx and tonsillar surfaces bilaterally 1
• If RADT negative in children/adolescents: Obtain backup throat culture (gold standard) 1
• If RADT negative in adults: Backup culture generally not necessary due to low rheumatic fever risk, but can be considered 1

When NOT to Test

• Do not test if viral features predominate: conjunctivitis, coryza, cough, hoarseness, discrete ulcerative stomatitis, viral exanthem, or diarrhea 1
• Generally avoid testing in children under 3 years unless risk factors present (e.g., older sibling with confirmed illness) 1

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First-Line Antibiotic Treatment

Penicillin V (phenoxymethylpenicillin) 250-500 mg orally every 6-8 hours for 10 days is the treatment of choice for scarlet fever, as it is cost-effective, has narrow spectrum activity, proven efficacy, and no documented resistance. 1, 2

Standard Dosing Regimens

• Adults: Penicillin V 500 mg orally twice daily OR 250 mg three times daily for 10 days 1
• Children: Amoxicillin 420 mg (20 mg/kg/dose) orally twice daily for 10 days is preferred over penicillin V due to better palatability 3
• Alternative once-daily dosing: Amoxicillin 840 mg (40 mg/kg) once daily is equally effective and may improve adherence 3

Critical Treatment Requirements

• Complete the full 10-day course even if symptoms resolve in 3-4 days—this is essential to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 3
• 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 appropriate antibiotic therapy 1

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Treatment for Penicillin-Allergic Patients

Non-Anaphylactic Penicillin Allergy

First-generation cephalosporins (cephalexin 500 mg orally twice daily for 10 days) are the preferred alternative for patients with non-immediate penicillin allergy, with only 0.1% cross-reactivity risk in delayed reactions. 3

• Cefadroxil 1 gram orally once daily for 10 days is an acceptable alternative 3
• These agents have strong, high-quality evidence supporting efficacy, narrow spectrum, and low cost 3

Immediate/Anaphylactic Penicillin Allergy

Clindamycin 300 mg orally three times daily for 10 days is the preferred choice for patients with immediate hypersensitivity (anaphylaxis, angioedema, urticaria within 1 hour), with only 1% resistance among Group A Streptococcus in the United States. 3

• Alternative macrolides: Azithromycin 500 mg orally once daily for 5 days OR clarithromycin 250 mg orally twice daily for 10 days 3
• Macrolide resistance is 5-8% in the United States and varies geographically—clindamycin is more reliable in areas with high resistance 3
• Do NOT use cephalosporins if patient had anaphylaxis, angioedema, or immediate urticaria to penicillin due to 10% cross-reactivity risk 3

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Symptomatic Management

• Antipyretics: Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms or high fever 3
• NEVER use aspirin in children under 16 years due to risk of Reye syndrome 1, 3
• Antipyretics provide symptomatic relief but do not replace the need for antibiotics 1

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Monitoring and Follow-Up

Expected Clinical Course

• Monitor for 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 Testing

• Routine post-treatment throat cultures are NOT recommended for asymptomatic patients who have completed therapy 1
• Consider follow-up testing only in special circumstances: history of rheumatic fever, community outbreak, or persistent symptoms 1

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Management of Household Contacts

Routine throat cultures or treatment for asymptomatic household contacts is generally not necessary, except in outbreak situations where all patients should be cultured and only those with positive results treated. 1, 2

• Approximately 25% of household contacts may harbor Group A Streptococcus asymptomatically 2
• In documented outbreaks (schools, day care centers), perform cultures for all patients and treat only those with positive results 2

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Critical Complications if Untreated

Early antibiotic treatment is essential to prevent serious sequelae, including suppurative complications (peritonsillar abscess, cervical lymphadenitis) and non-suppurative complications (acute rheumatic fever, acute glomerulonephritis). 1

• Invasive Group A Streptococcus infections with toxic shock syndrome are rare but life-threatening complications requiring urgent recognition 4, 5
• Toxic scarlet fever complicating cellulitis can mimic drug eruption—early clinical diagnosis is crucial to prevent fatal outcome 5

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Common Pitfalls to Avoid

• Do NOT prescribe shorter courses than 10 days (except azithromycin's 5-day regimen)—this dramatically increases treatment failure and rheumatic fever risk 3
• Do NOT assume all penicillin-allergic patients cannot receive cephalosporins—only those with immediate/anaphylactic reactions should avoid them 3
• Do NOT use trimethoprim-sulfamethoxazole (Bactrim)—sulfonamides do not eradicate Group A Streptococcus and are associated with increased disease severity 1, 3
• Do NOT delay surgical consultation if necrotizing infection is suspected—antibiotics alone are insufficient 6