Kawasaki Disease versus Rheumatic Fever: Key Distinctions
Kawasaki disease and acute rheumatic fever are fundamentally different diseases—Kawasaki disease is an acute self-limited vasculitis of unknown etiology affecting predominantly infants and young children (median age 2 years) with coronary artery involvement, while rheumatic fever is a post-streptococcal autoimmune condition that has been replaced by Kawasaki disease as the leading cause of acquired heart disease in children in developed countries. 1, 2
Age and Demographics
Kawasaki Disease:
- Predominantly affects children younger than 5 years old, with 76% of cases occurring in this age group and a median age of 2 years 1, 2
- Boys outnumber girls by 1.5 to 1.7:1 1
- Highest incidence in children of Asian and Pacific Island descent (32.5/100,000), intermediate in African Americans (16.9/100,000) and Hispanics (11.1/100,000), and lowest in whites (9.1/100,000) 1
Rheumatic Fever:
- Typically affects school-age children (5-15 years old), which is notably older than the Kawasaki disease population 3
Clinical Presentation
Kawasaki Disease requires fever ≥5 days PLUS 4 of 5 principal features: 1, 2
- Bilateral nonexudative conjunctivitis (bulbar, without limbus involvement) 1, 2
- Oral changes: erythema of lips and oral mucosa, cracking of lips, strawberry tongue 1, 2
- Polymorphous rash (maculopapular, urticarial, or scarlatiniform) 1, 2
- Extremity changes: acute phase shows erythema and edema of hands/feet; subacute phase (2-3 weeks later) shows periungual desquamation 1, 2
- Cervical lymphadenopathy (usually unilateral, ≥1.5 cm) 1, 2
Critical distinguishing features that suggest NOT Kawasaki disease: 1
- Exudative conjunctivitis
- Exudative pharyngitis
- Discrete intraoral lesions
- Bullous or vesicular rash
- Generalized adenopathy
Pathophysiology and Cardiac Involvement
Kawasaki Disease:
- An acute systemic vasculitis affecting medium-sized arteries throughout the body 1, 2
- Coronary artery aneurysms or ectasia develop in 15-25% of untreated children, which can lead to myocardial infarction, sudden death, or ischemic heart disease 1, 2
- Three distinct pathological processes: necrotizing arteritis (first 2 weeks), subacute/chronic vasculitis (months to years), and luminal myofibroblastic proliferation causing progressive stenosis 2
- Involves activation of IL-1, IL-6, and TNF signaling pathways 2
Rheumatic Fever:
- A post-streptococcal autoimmune condition with different cardiac manifestations (valvular disease rather than coronary artery involvement) 3
Epidemiology and Seasonality
Kawasaki Disease:
- More common during winter and early spring months 1
- Occurs in both endemic and epidemic forms with wave-like geographic spread 1
- Case fatality rate of 0.08% in Japan 1
- An estimated 4,248 hospitalizations in the United States in 2000 1
Treatment Implications
Kawasaki Disease:
- Treatment with intravenous immunoglobulin (IVIG) 2 g/kg plus aspirin reduces coronary artery abnormalities from 20% to 4% 1
- Must be treated within 10 days of fever onset to prevent coronary complications 1
- Treatment is directed at reducing inflammation in coronary artery walls and preventing coronary thrombosis 1
Common Pitfalls
- Delayed diagnosis of Kawasaki disease in older children who may have higher prevalence of cardiovascular complications 1
- Clinical features may not all be present simultaneously—careful history-taking over the entire illness course is essential 2
- Incomplete Kawasaki disease can occur with fewer than 4 classic criteria but still requires treatment if coronary abnormalities are detected on echocardiography 2
- Pediatricians in developed nations may miss rheumatic fever due to its comparative rarity, as highlighted by a case where both conditions occurred sequentially in the same patient 3