Rheumatic Fever

Definition

Multisystem autoimmune disease, follows Group A Strep (S. pyogenes) pharyngitis. All manifestations resolve EXCEPT cardiac valve damage = Rheumatic Heart Disease (RHD).

Pathogenesis

Age: 5-14 years (primary), rare >30. Recurrence more common in adolescents/young adults. Gender: no clear ARF association; RHD more common in FEMALES.

Rheumatogenic M-serotypes: 1, 3, 5, 6, 14, 18, 19, 24, 27, 29. Genetic: HLA-DR7, HLA-DR4 = ↑susceptibility.

Mechanisms:

• Molecular mimicry (autoimmune theory): anti-M-protein Ab cross-reacts with heart/joint tissue → binds valvular endothelium → damage
• Cytotoxic theory: strep toxins (pyrogenic toxin) + streptolysin O = direct cardiac toxicity

Clinical Manifestations (~3wk post-strep infection, often subclinical)

Order of frequency:

1. Migratory polyarthritis (COMMONEST) — hot/swollen/red/tender, migrates over hours, asymmetric, large joints (knee/ankle/hip/elbow)
2. Pancarditis — endocardium/pericardium/myocardium. Valvular damage = HALLMARK. MR = commonest lesion. Myocardial → prolonged PR interval.
3. Subcutaneous nodules — painless, mobile, bony prominences
4. Sydenham’s chorea — involuntary movement, head+limbs
5. Erythema marginatum — pink macular rash, appears/fades visibly

Diagnosis — Revised Jones Criteria (2015)

Stratified by risk population (NEW in 2015):

Diagnostic threshold:

• Initial ARF: 2 major OR 1 major+2 minor
• Recurrent ARF (reliable past hx): 2 major OR 1major+2minor OR 3 minor

1992 criteria required supporting evidence of prior strep infection (↑ASO, +throat culture, rapid Ag test, recent scarlet fever) within 45 days — REMOVED in 2015 revision.

Treatment

Penicillin DOC — oral (Pen V/amoxicillin ×10 days) OR single IM benzathine penicillin G 1.2 million units. Supportive: aspirin (arthritis/arthralgia/fever).

Prevention

Primary: prompt complete antibiotic Rx of GAS sore throat within 9 days → prevents almost ALL ARF.

Secondary (MAINSTAY of RHD control): long-term penicillin prophylaxis. DOC: IM benzathine penicillin G every 4 weeks. Alternative (penicillin allergy): oral erythromycin 250mg BD.

Duration by carditis severity:

• No carditis: 5 years post-attack OR age 21 (longer)
• Carditis, no residual valve disease: 10 years post-attack OR age 21 (longer)
• Persistent valvular disease: 10 years post-attack OR age 40 (longer), sometimes LIFELONG

What Acute Rheumatic Fever Is

Acute rheumatic fever (ARF) is a multisystem autoimmune disease that follows group A streptococcal (S. pyogenes) pharyngitis. Nearly every manifestation resolves completely — the single, critical exception being cardiac valve damage, which persists as rheumatic heart disease (RHD). S. pyogenes itself principally causes skin and soft tissue infection; ARF is what happens when a throat infection with the wrong strain triggers an immune response that goes on to attack the heart.

Pathogenesis

Primary ARF is mainly a disease of children aged 5–14 years and is rare beyond 30, though recurrent episodes are more common in adolescents and young adults. There is no clear gender association for ARF itself, but RHD affects females more often.

ARF follows upper respiratory infection with specific rheumatogenic group A streptococcal M-serotypes (1, 3, 5, 6, 14, 18, 19, 24, 27, 29) — not every strain carries equal risk. Genetic susceptibility plays a real role: people carrying HLA-DR7 and HLA-DR4 are more prone.

The underlying mechanism is not fully settled, but two contributing theories are well established:

• Molecular mimicry (autoimmune theory): antibodies raised against the streptococcal M protein cross-react with human tissue antigens — heart and joint — because the two structures resemble each other closely enough to fool the immune system. These cross-reactive antibodies bind valvular endothelium directly, causing the damage that defines RHD.
• Cytotoxic theory: streptococcal toxins (streptococcal pyrogenic toxin) and enzymes (streptolysin O) are directly toxic to cardiac tissue, independent of any cross-reactive antibody.

Clinical Manifestations

Manifestations typically appear about 3 weeks after the precipitating streptococcal infection, which may have been subclinical (more common) or presented as overt sore throat. ARF affects heart, joints, skin, and brain, in roughly this order of frequency:

• Migratory polyarthritis — the commonest manifestation: hot, swollen, red, tender joints that migrate from one joint to another over hours. Asymmetric, affecting large joints — most commonly knees, ankles, hips, and elbows.
• Pancarditis — affecting endocardium, pericardium, or myocardium. Valvular damage is the hallmark finding, with mitral regurgitation the commonest lesion (aortic regurgitation also occurs). Myocardial inflammation can disturb the electrical conduction system, producing P-R interval prolongation.
• Subcutaneous nodules — painless, small, mobile lumps beneath the skin over bony prominences, particularly hands, feet, and elbows.
• Sydenham’s chorea — an abnormal involuntary movement disorder, mainly affecting the head and limbs.
• Erythema marginatum — pink macular rashes that visibly appear and fade before the examiner’s eyes.

Diagnosis: Revised Jones Criteria (2015)

Diagnosis uses the 2015 revision of the Jones criteria, which — for the first time — stratifies criteria by whether the patient comes from a low-risk or high-risk (ARF-endemic) population, since the same threshold doesn’t perform equally well in both settings.

Diagnostic thresholds:

• Initial ARF: 2 major, or 1 major + 2 minor.
• Recurrent ARF (with a reliable past history of ARF/RHD): 2 major, or 1 major + 2 minor, or 3 minor criteria.

The 1992 version of the Jones criteria required supporting evidence of a preceding streptococcal infection within 45 days (elevated ASO titre — substantially higher in ARF than in uncomplicated GAS infection — a positive throat culture, a rapid GAS antigen test, or recent scarlet fever) as a mandatory element. The 2015 revision has dropped this as a formal requirement.

Treatment

Penicillin is the drug of choice — either oral (penicillin V or amoxicillin for 10 days) or a single intramuscular dose of benzathine penicillin G (1.2 million units). Supportive treatment (aspirin) manages arthritis, arthralgia, and fever.

Prevention

Primary prevention is straightforward and highly effective: timely, complete antibiotic treatment (penicillin) of group A streptococcal sore throat, started within 9 days of symptom onset, prevents almost all cases of ARF.

Secondary prevention is the actual mainstay of controlling ARF and RHD at the population level, because a patient who has already had one episode of ARF carries a much higher risk of a recurrence — and each recurrence adds further cumulative valve damage. Long-term penicillin prophylaxis is therefore indicated: intramuscular benzathine penicillin G every 4 weeks is the drug of choice, with oral erythromycin (250 mg twice daily) as the alternative for penicillin allergy. Duration is set by the severity of the index episode’s cardiac involvement:

• ARF without carditis: 5 years after the last attack, or until age 21, whichever is longer.
• ARF with carditis but no residual valvular disease: 10 years after the last attack, or until age 21, whichever is longer.
• ARF with persistent valvular disease: 10 years after the last attack, or until age 40, whichever is longer — sometimes extended to lifelong prophylaxis.

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