What is the best course of action for a patient with a history of juvenile rheumatic fever and mononucleosis, presenting with fever, chest pain, and mid upper quadrant abdominal pain?

Immediate Diagnostic and Management Approach

This patient requires urgent evaluation for acute rheumatic fever recurrence with possible pericarditis, and should be transported to the emergency department immediately for ECG, cardiac troponin, echocardiography, and initiation of penicillin therapy with anti-inflammatory treatment. 1, 2

Initial Emergency Assessment

Critical First Steps (Within 10 Minutes)

• Obtain 12-lead ECG immediately to evaluate for ST-segment changes, pericarditis patterns, or myocarditis 1
• Measure cardiac troponin as soon as possible to assess for myocardial involvement 1
• Perform focused cardiovascular examination looking for:
  • Pericardial friction rub (suggests pericarditis) 1
  • New or changed heart murmurs (mitral regurgitation or aortic regurgitation from acute rheumatic carditis) 1
  • Signs of heart failure (S3 gallop, crackles, tachycardia) 1
  • Fever and pleuritic chest pain worsened by supine position (pericarditis) 1

Abdominal Examination Specifics

• Assess right upper quadrant for Murphy's sign and hepatomegaly (occurs in 10% of mononucleosis cases and can cause mid-upper quadrant pain) 3, 4
• Palpate for splenomegaly (present in 50% of mononucleosis; splenic rupture occurs in 0.1-0.5% and is life-threatening) 3, 4
• Evaluate for peritoneal signs that would suggest splenic rupture or other acute abdominal pathology 3

Differential Diagnosis Priority

Most Likely: Acute Rheumatic Fever Recurrence with Pericarditis

This patient's history of juvenile rheumatic fever places them at high risk for recurrence, particularly if they were not on adequate secondary prophylaxis. The combination of fever, chest pain, and the temporal relationship to mononucleosis (which can trigger immune dysregulation) suggests acute rheumatic carditis with pericardial involvement 2, 5, 6.

Alternative Considerations

• Viral myopericarditis from Epstein-Barr virus: Mononucleosis can directly cause myopericarditis, presenting with severe chest pain 1, 5
• Hepatobiliary pathology: Right upper quadrant pain with fever could represent hepatitis (common in mononucleosis) or cholecystitis 1, 3
• Splenic complications: Mid-upper quadrant pain could indicate splenic capsular distension or early rupture 3, 4

Immediate Diagnostic Workup

Laboratory Testing

• Complete blood count with differential: Look for >40% lymphocytes and >10% atypical lymphocytes (supports active mononucleosis) 4
• Liver enzymes (AST, ALT): Elevated in mononucleosis and increases suspicion if heterophile test is negative 4
• Heterophile antibody test (Monospot): Sensitivity 87%, specificity 91% for mononucleosis 4
• Anti-streptolysin O (ASO) or anti-DNase B titers: Essential for documenting antecedent streptococcal infection in rheumatic fever 2, 6
• Inflammatory markers (ESR, CRP): Elevated in both rheumatic fever and viral infections 2

Imaging Studies

• Echocardiography: Mandatory to assess for valvular involvement, pericardial effusion, and ventricular function 1, 2
• CT abdomen/pelvis with IV contrast: If abdominal pain is prominent and splenic pathology is suspected, this is the most appropriate initial imaging 1
• Chest X-ray: Evaluate for cardiomegaly, pulmonary edema, or pneumonia 1

Treatment Algorithm

Phase 1: Antimicrobial Therapy (Initiate Immediately)

Regardless of throat culture results, start full therapeutic course of penicillin to eradicate residual Group A Streptococcus: 2

• Penicillin V oral: 500 mg 2-3 times daily for 10 days (adolescents/adults) 2
• Alternative for penicillin allergy: Erythromycin or first-generation cephalosporin (if no immediate-type hypersensitivity) 2

Phase 2: Anti-Inflammatory Therapy

For rheumatic fever with carditis/pericarditis: 2

• Prednisone 1-2 mg/kg/day for 1-2 weeks if severe inflammation or cardiac involvement is present 2
• For pericardial chest pain specifically: NSAIDs (ibuprofen or indomethacin) can be added for symptom relief 1
• Low-dose colchicine may be added for persistent pericardial pain 1

Critical caveat: Avoid aspirin in patients with recent mononucleosis if under 16 years old due to Reye's syndrome risk 7

Phase 3: Secondary Prophylaxis (Start Before Discharge)

Given this patient's history of rheumatic fever, lifelong prophylaxis is likely indicated: 1, 2, 8

• Benzathine penicillin G 1.2 million units IM every 4 weeks (preferred regimen, Class I evidence) 1, 2, 8
• Consider every 3-week dosing if this represents a recurrence despite previous prophylaxis 1, 2, 8
• Duration: For patients with rheumatic carditis and residual heart disease, continue for 10 years after last episode or until age 40 (whichever is longer), potentially lifelong 1, 2, 8

Activity Restrictions

For Mononucleosis with Splenomegaly

Strict avoidance of contact sports and strenuous exercise for 8 weeks or until splenomegaly resolves to prevent splenic rupture 3, 4

For Rheumatic Carditis

Activity restriction based on cardiac involvement severity; patients with active carditis require bed rest as tolerated until inflammation resolves 2, 9

Critical Pitfalls to Avoid

1. Do not delay penicillin therapy waiting for throat culture results—at least one-third of rheumatic fever cases arise from asymptomatic streptococcal infections 2, 8

2. Do not rely solely on heterophile antibody testing in the first week of mononucleosis illness (can be false-negative); if clinical suspicion is high and test is negative, check EBV viral capsid antigen antibodies 4

3. Do not assume chest pain is benign in a patient with rheumatic fever history—myopericarditis can be life-threatening and requires immediate cardiac evaluation 1, 5

4. Do not discharge without ensuring secondary prophylaxis is established—recurrence risk is highest in patients with previous rheumatic fever, and benzathine penicillin G is 10 times more effective than oral antibiotics (0.1% vs 1% recurrence rate) 8

5. Do not perform palpation of the spleen if splenic rupture is suspected—this can precipitate complete rupture 3

Disposition and Follow-Up

Hospitalization is recommended for patients with suspected rheumatic carditis, ideally at a center with cardiology expertise 1, 2. Outpatient management may be considered only if:

• Cardiac evaluation is completely normal
• No evidence of significant pericardial effusion or myocarditis
• Abdominal examination is benign without splenomegaly
• Reliable follow-up within 24-48 hours is ensured 7

Follow-up cardiac imaging (echocardiography or CMR) at 3-6 months is recommended to assess for residual valvular disease, which determines duration of prophylaxis 1, 2