11.4 Rheumatic Fever & Acquired Heart Disease

Acute Rheumatic Fever and Group A Streptococcus

Acute rheumatic fever (ARF) is an autoimmune, multisystem inflammatory illness that follows group A Streptococcus (GAS, Streptococcus pyogenes) pharyngitis — never a skin or soft tissue GAS infection — typically 2–4 weeks after an untreated or inadequately treated strep throat. Molecular mimicry between GAS antigens and human cardiac, joint, and central nervous system tissue drives the antibody-mediated damage. ARF remains an important cause of acquired heart disease across the Arab League region, where moderate-to-high ARF and rheumatic heart disease incidence is common — relevant context for this exam, since the moderate/high-risk diagnostic thresholds (rather than the low-risk thresholds used in North America and Western Europe) are often the more clinically applicable set.

Modified Jones Criteria (2015 Revision)

Diagnosis of an initial episode of ARF requires evidence of a preceding GAS infection (a positive throat culture or rapid antigen test, or elevated/rising streptococcal antibody titers such as ASO) plus either 2 major criteria, or 1 major criterion plus 2 minor criteria.

Major criteria (mnemonic: JONES):

Minor criteria include fever (38.5°C or higher), elevated inflammatory markers (ESR 30 mm/hr or higher, or CRP 3.0 mg/dL or higher, in moderate/high-risk populations; a higher ESR threshold of 60 mm/hr or more applies in low-risk populations), polyarthralgia (only if polyarthritis is not already counted as major), and a prolonged PR interval on ECG (only if carditis is not already counted as major).

Carditis is the most clinically important manifestation because, unlike arthritis or chorea, it can leave permanent valvular scarring. Recurrent, untreated, or poorly treated episodes progress to chronic rheumatic heart disease, classically causing mitral stenosis years to decades later. Treatment of an acute episode combines a full course of penicillin (to eradicate any residual GAS), anti-inflammatory therapy (aspirin or NSAIDs for arthritis and carditis), and — critically — long-term secondary prophylaxis with intramuscular benzathine penicillin G every 3–4 weeks to prevent recurrences, since each recurrence compounds cumulative valvular damage.

Secondary prophylaxis duration is a frequent board-style question. After an initial ARF episode — especially with carditis — benzathine penicillin G continues for a prolonged period, generally until age 21 or at least 10 years after the last episode, whichever is longer; longer durations may be appropriate when established rheumatic heart disease is present. Every episode of untreated streptococcal pharyngitis can trigger recurrence and further valve injury, which is why sore-throat recognition, household contact treatment, and adherence counseling matter in endemic regions across the Arab League.

Kawasaki Disease

Kawasaki disease (KD) is an acute, self-limited medium-vessel vasculitis of unknown etiology, occurring predominantly in children under 5 years, and is a leading cause of acquired heart disease in children. Diagnosis is clinical, based on fever for 5 days or more plus at least 4 of 5 principal criteria (mnemonic CRASH):

• Conjunctivitis — bilateral, non-exudative (bulbar)
• Rash — polymorphous (not vesicular or bullous)
• Adenopathy — cervical lymphadenopathy, usually unilateral, 1.5 cm or larger
• Strawberry tongue and oral changes — red, cracked lips, strawberry tongue, oral mucosal erythema
• Hand-foot changes — erythema and edema of the palms and soles acutely, followed by periungual desquamation 1–3 weeks later

Infants under 6 months and children who do not meet the full clinical criteria can have incomplete (atypical) Kawasaki disease, which still carries a real — and sometimes higher — risk of coronary involvement, so a high index of suspicion with supportive labs and echocardiography is essential in a young infant with prolonged, unexplained fever.

Treatment and coronary risk are the highest-yield facts:

• IVIG (intravenous immunoglobulin), 2 g/kg as a single infusion, ideally given within 10 days of fever onset, dramatically reduces coronary aneurysm risk
• High-dose aspirin, 80–100 mg/kg/day divided, during the acute febrile phase, then low-dose (antiplatelet) aspirin, 3–5 mg/kg/day, continued until follow-up echocardiography confirms no coronary involvement (Kawasaki disease is one of the few pediatric indications for aspirin despite the usual Reye syndrome concern)
• Untreated, coronary artery aneurysm risk is roughly 25%; timely IVIG treatment lowers that risk to roughly 4–5%
• Echocardiography is obtained at diagnosis, at 1–2 weeks, and again at 6–8 weeks to track coronary artery status, using Z-scores to grade aneurysm severity
• An IVIG-resistant (refractory) case — persistent or recrudescent fever after the first infusion, seen in roughly 10–20% of patients — requires a second IVIG dose or adjunctive corticosteroids

Kawasaki disease and rheumatic fever are commonly confused on exams because both can present with fever, rash, and joint symptoms in a school-aged or younger child. The distinguishing anchors are the conjunctivitis, mucositis, extremity changes, and coronary artery involvement of Kawasaki disease versus the migratory polyarthritis, documented preceding GAS infection, and valvulitis of rheumatic fever.