What is the likely diagnosis and management for a 5-year-old child with two weeks of high fevers, severe joint pains, and swelling of the knees and elbows, following a recent sore throat, and treated with benzathine penicillin G (penicillin G benzathine)?

Acute Rheumatic Fever Following Group A Streptococcal Pharyngitis

This 5-year-old child most likely has acute rheumatic fever (ARF) as a post-streptococcal complication, and the administration of intramuscular benzathine penicillin G was the correct initial treatment to eradicate any residual streptococcal infection and prevent further cardiac damage. 1

Clinical Diagnosis

The clinical presentation strongly suggests acute rheumatic fever based on:

• Temporal relationship: Sore throat 4 weeks ago followed by new symptoms 2 weeks later, fitting the typical 2-4 week latency period between Group A streptococcal (GAS) pharyngitis and ARF 1
• High-grade fever: Temperatures up to 40°C persisting for two weeks 1
• Migratory polyarthritis: Severe joint pains with significant intermittent swelling of large joints (knees and elbows), which is a major Jones criterion for ARF 1
• Age appropriateness: While ARF is rare in children under 3 years, this 5-year-old falls within the typical age range (5-15 years) for initial ARF attacks 1

Immediate Management Already Initiated

The single dose of intramuscular benzathine penicillin G was appropriate and necessary to:

• Eradicate any residual GAS from the pharynx 1, 2
• Prevent ongoing streptococcal antigenic stimulation that could worsen the autoimmune response 1
• Serve as the first step in what will become long-term secondary prophylaxis 2, 3

Penicillin remains the only antibiotic proven in controlled trials to prevent rheumatic fever and has never demonstrated resistance in GAS 2

Additional Acute Management Required

Beyond the penicillin already given, this child needs:

• Anti-inflammatory therapy: High-dose aspirin or NSAIDs for arthritis and fever control, as adjunctive therapy is often useful in managing GAS-related complications 1
• Cardiac evaluation: Echocardiogram to assess for carditis (the most serious manifestation of ARF that determines long-term prognosis) 1
• Complete Jones criteria assessment: Evaluate for other major criteria (carditis, chorea, erythema marginatum, subcutaneous nodules) and minor criteria (fever, arthralgia, elevated acute phase reactants, prolonged PR interval) 1
• Streptococcal serology: Anti-streptolysin O (ASO) or anti-DNase B titers to document recent streptococcal infection 1

Long-Term Secondary Prophylaxis

This child will require continuous antimicrobial prophylaxis for years to prevent recurrent ARF, which carries high risk of progressive cardiac damage 2, 3:

• Benzathine penicillin G 1.2 million units intramuscularly every 3-4 weeks is the gold standard for secondary prophylaxis 2, 3, 4
• Evidence suggests 3-week intervals are superior to 4-week intervals for high-risk patients, with significantly fewer recurrences (P = 0.01) 4
• Duration of prophylaxis depends on cardiac involvement: minimum 5 years or until age 21 (whichever is longer) for ARF without carditis; 10 years or until age 21 for ARF with carditis without residual heart disease; lifelong for those with persistent rheumatic heart disease 1, 2

Critical Pitfalls to Avoid

• Do not delay treatment waiting for confirmatory tests: Treatment within 9 days of symptom onset still effectively prevents ARF progression, but this child is already symptomatic with ARF 2
• Do not test or treat asymptomatic household contacts: Prophylactic treatment of contacts is not recommended and has not been shown to reduce subsequent GAS pharyngitis incidence 1
• Do not perform follow-up throat cultures after completing acute treatment unless symptoms recur, as positive tests may simply reflect carrier status rather than active infection 1, 5
• Recognize that adherence to long-term prophylaxis is challenging: The need for painful injections every 3-4 weeks for years is a major barrier, requiring close follow-up and family education 3

Prognosis and Monitoring

The arthritis of ARF typically resolves completely without sequelae, but cardiac involvement determines long-term outcomes 1. Regular cardiac monitoring is essential, as recurrent episodes of ARF (which occur in up to 50% without prophylaxis) cause cumulative cardiac damage 1, 2. With appropriate secondary prophylaxis, recurrence rates drop dramatically—studies show no recurrences in compliant patients on 3-weekly benzathine penicillin 6, 4.