What is Kawasaki disease?

Kawasaki Disease

Kawasaki disease is an acute, self-limiting systemic vasculitis that predominantly affects the coronary arteries in children, representing the leading cause of acquired heart disease among children in developed countries. 1, 2

Definition and Epidemiology

• First described in 1967 by Tomisaku Kawasaki
• Primarily affects children under 5 years of age
• Higher incidence in children of Asian descent:
  • Japanese children: ~150 per 100,000 children under 5 years
  • United States: ~10-15 per 100,000 children under 5 years 2
• Etiology remains unknown, though an infectious trigger with genetic predisposition is strongly suspected 1

Diagnostic Criteria

Diagnosis is based on clinical criteria, requiring fever for ≥5 days plus 4 of the following 5 principal features:

1. Bilateral non-exudative conjunctival injection - typically spares the limbus, without photophobia or eye pain
2. Oral mucosal changes - erythema and cracking of lips, strawberry tongue, diffuse erythema of oral and pharyngeal mucosa (without focal lesions or ulcerations)
3. Polymorphous rash - primarily truncal, often accentuated in the groin, typically maculopapular
4. Extremity changes - erythema and edema of hands and feet in acute phase with sharp demarcation at wrists/ankles, followed by periungual desquamation in convalescent phase
5. Cervical lymphadenopathy - usually unilateral, ≥1.5 cm diameter, confined to anterior cervical triangle 1

Laboratory Findings

• Elevated inflammatory markers:
  • ESR >40 mm/hr
  • CRP >3 mg/dL
• Leukocytosis (WBC >15,000/mm³) with left shift
• Mild anemia
• Hypoalbuminemia
• Elevated liver enzymes
• Sterile pyuria
• Thrombocytosis (typically in second week of illness) 1

Treatment Algorithm

Initial Treatment

1. IVIG 2 g/kg as a single infusion plus high-dose aspirin (80-100 mg/kg/day divided QID) 1
2. Treatment should be initiated within 10 days of fever onset when possible
3. Continue high-dose aspirin until patient is afebrile for 48-72 hours
4. Reduce to low-dose aspirin (3-5 mg/kg/day) for antiplatelet effect

For IVIG Non-responders (10-20% of patients)

1. Second dose of IVIG 2 g/kg 3
2. Consider adding corticosteroids, especially in high-risk patients
3. For refractory cases: consider infliximab, cyclosporine, or methotrexate 3

Duration of Aspirin Therapy

• Without coronary abnormalities: continue low-dose aspirin for 6-8 weeks
• With coronary abnormalities: continue aspirin indefinitely 1
• Avoid ibuprofen as it antagonizes aspirin's antiplatelet effect 1

Cardiac Monitoring

• Echocardiography schedule:
  • At diagnosis
  • Within 1-2 weeks of treatment
  • 4-6 weeks after treatment
• More frequent monitoring for patients with coronary abnormalities 1

Special Considerations

Incomplete/Atypical Kawasaki Disease

• Presents with fever ≥5 days plus 2-3 of the principal features
• Carries same risk of coronary complications as classic disease
• Approximately 5% develop coronary artery dilation and 1% develop giant aneurysms even with optimal treatment 1

High-Risk Populations

• Infants <6 months are at particularly high risk for coronary abnormalities
• Often present with prolonged fever as the sole clinical finding
• Require lower threshold for evaluation and treatment 1

Complications and Long-term Management

• Coronary artery aneurysms occur in approximately 25% of untreated patients and 4.7% of properly treated patients 4
• Potential complications include:
  • Myocardial infarction
  • Ischemic heart disease
  • Sudden death 2
• Long-term management based on degree of coronary involvement:
  • Without coronary abnormalities: cardiovascular risk factor counseling every 5 years
  • With transient coronary ectasia: counseling every 3-5 years
  • With persistent coronary abnormalities: ongoing antiplatelet therapy, activity restrictions, and cardiac monitoring 1

Preventative Measures

• Annual influenza vaccination for children on long-term aspirin therapy (to reduce Reye syndrome risk)
• Defer measles and varicella immunizations for 11 months after high-dose IVIG administration 1

Prompt diagnosis and early treatment are crucial to reduce the risk of coronary complications in Kawasaki disease. The clinical presentation can be variable, and clinicians should maintain a high index of suspicion, particularly in infants who may present with incomplete features.