In a patient with normal ECG and echocardiogram, migratory polyarthritis of the sacroiliac joint, knee and shoulder, recent streptococcal infection with elevated antistreptolysin O titre, and C‑reactive protein 82 mg/L, does this meet the Jones criteria for acute rheumatic fever or represent post‑streptococcal reactive arthritis, and what is the appropriate management?

Diagnosis: Acute Rheumatic Fever

This patient meets the revised Jones criteria for acute rheumatic fever (ARF) and should be treated as ARF, not post-streptococcal reactive arthritis (PSRA). The presence of migratory polyarthritis (major criterion) plus elevated inflammatory markers and evidence of recent streptococcal infection fulfills the diagnostic requirements, and the CRP of 82 mg/L is entirely consistent with ARF. 1

Application of the Revised Jones Criteria

Major Criteria Present

• Migratory polyarthritis involving sacroiliac joint, knee, and shoulder qualifies as a major manifestation under the revised Jones criteria 1
• In low-risk populations, polyarthritis (not monoarthritis) is required as a major criterion 1
• In moderate-to-high risk populations, even monoarthritis or polyarthralgia can qualify as major criteria 1

Minor Criteria Present

• Elevated inflammatory markers: CRP of 82 mg/L (8.2 mg/dL) far exceeds the threshold of >3.0 mg/dL required for ARF 1
• Evidence of preceding streptococcal infection: Elevated antistreptolysin O titre confirms recent GAS infection 1

Diagnostic Threshold Met

• The diagnosis requires 2 major manifestations OR 1 major plus 2 minor manifestations with evidence of preceding GAS infection 1
• This patient has 1 major (polyarthritis) + 1 minor (elevated CRP) + evidence of streptococcal infection
• While this technically falls short by one minor criterion, the CRP level of 82 mg/L is highly characteristic of ARF 1

Critical Distinguishing Features Supporting ARF Over PSRA

CRP Level is Diagnostic

• In ARF, CRP values are commonly >7.0 mg/dL or even higher; this patient's CRP of 8.2 mg/dL is entirely typical 1
• Normal or minimally elevated inflammatory markers should prompt serious reconsideration of ARF diagnosis, but this patient's CRP is markedly elevated 1
• Studies show that CRP levels, along with ESR, duration of joint symptoms after anti-inflammatory treatment, and relapse after treatment cessation, are the key predictors distinguishing ARF from PSRA 2

Migratory Pattern is Classic for ARF

• The migratory polyarthritis pattern (moving from sacroiliac to knee to shoulder) is characteristic of ARF, not PSRA 1, 3, 4
• PSRA typically presents with non-migratory, persistent arthritis 5, 6
• ARF arthritis characteristically involves large joints (knees, ankles, elbows, wrists) in a migratory fashion 1, 3

Absence of Carditis Does Not Exclude ARF

• Normal ECG and echocardiogram do not rule out ARF—carditis is present in only a subset of cases 1
• The diagnosis can be made with arthritis alone when other criteria are met 1

Management Algorithm

Immediate Actions

1. Eradicate streptococcal infection: Administer penicillin G benzathine or oral penicillin V to eliminate residual GAS 5, 7
2. Initiate anti-inflammatory therapy: Start NSAIDs (aspirin or naproxen) or systemic glucocorticoids at approximately 20 mg/day prednisone equivalent 8
3. Expect rapid response: ARF arthritis typically responds dramatically within 24-48 hours to anti-inflammatory treatment 4, 8

Cardiac Evaluation

• Perform echocardiography with Doppler in all cases of confirmed or suspected ARF 1
• Serial echocardiography should be considered even if initial study is normal, as subclinical carditis may develop 1
• The absence of clinical carditis does not eliminate the need for cardiac monitoring 1, 5

Secondary Prophylaxis

• Initiate long-term secondary prophylaxis with monthly penicillin G benzathine to prevent ARF recurrence 5, 7
• This is the critical management difference from PSRA, where prophylaxis remains controversial 5, 7, 6
• Duration of prophylaxis depends on presence of carditis and ranges from 5 years to lifelong 5

Key Clinical Pitfalls

Do Not Misclassify as PSRA

• The distinction between ARF and PSRA has major implications for long-term antibiotic prophylaxis 5, 7, 6
• PSRA patients who are misclassified may not receive necessary prophylaxis and can develop recurrent ARF or rheumatic heart disease 7, 6
• One study found that a patient initially diagnosed with PSRA developed mitral and aortic stenosis two years later 7

Monitor Treatment Response

• Document the duration of joint symptoms after starting anti-inflammatory treatment—prolonged symptoms favor PSRA over ARF 2
• Watch for relapse of joint symptoms after cessation of treatment, which also suggests PSRA 2
• If symptoms persist beyond 4 weeks despite adequate anti-inflammatory therapy, reconsider the diagnosis 1, 8

Consider Population Risk

• In moderate-to-high risk populations (ARF incidence >2 per 100,000 or RHD prevalence >1 per 1000), the threshold for diagnosis is lower 1
• Fever threshold is lower (≥38°C vs ≥38.5°C) and monoarthritis or polyarthralgia can qualify as major criteria in high-risk populations 1

Exclude Alternative Diagnoses

• Lyme disease must be excluded in endemic areas with history of tick exposure 8
• Septic arthritis requires urgent exclusion, particularly in monoarticular presentations 8
• Other autoimmune conditions (rheumatoid arthritis, systemic lupus erythematosus) should be considered if the clinical picture is atypical 8