What is Kawasaki disease and its main characteristics?

Kawasaki Disease: Definition and Key Characteristics

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

Definition and Epidemiology

• Kawasaki disease was first described in Japan in 1967 by Tomisaku Kawasaki and has replaced acute rheumatic fever as the leading cause of acquired heart disease in children in developed countries 1
• It primarily affects children younger than 5 years of age 1
• Higher incidence is observed in children of Asian descent, particularly Japanese (150 per 100,000 children under five years in Japan versus 10-15 per 100,000 in the United States) 1
• The etiology remains unknown despite decades of research, though an infectious trigger with genetic predisposition is strongly suspected 1

Classic Diagnostic Criteria

Diagnosis is based on the presence of fever for at least 5 days plus 4 of the following 5 principal clinical features 1:

• Fever: Typically high-spiking (>102.2°F/39°C, often >104°F/40°C) and persists for an average of 11 days if untreated 1
• Bilateral bulbar conjunctival injection: Non-exudative, without limbus involvement, photophobia or eye pain 1
• Changes in the lips and oral mucosa: Erythema, cracking of lips, strawberry tongue, diffuse oral and pharyngeal redness 1
• Polymorphous exanthem/rash: Various forms including maculopapular, urticarial, or scarlatiniform 1
• Changes in extremities: Acute phase - erythema and edema of hands and feet; subacute phase - periungual desquamation (peeling) of fingers and toes typically beginning 2-3 weeks after fever onset 1
• Cervical lymphadenopathy: Usually unilateral, ≥1.5 cm diameter 1

Incomplete/Atypical Kawasaki Disease

• Diagnosed in patients with fever ≥5 days and 2-3 principal features 1, 2
• Carries similar risk of coronary complications as classic disease 1
• More common in infants under 6 months 1
• Requires high index of suspicion and often supplemental laboratory criteria 1

Pathophysiology

• Systemic inflammation affects medium-sized arteries throughout the body 1
• Three pathological processes have been identified 1:
  1. Necrotizing arteritis (self-limited, within first 2 weeks)
  2. Subacute/chronic vasculitis (can persist for months to years)
  3. Luminal myofibroblastic proliferation (can cause progressive arterial stenosis)
• Activation of both innate and adaptive immune systems with evidence of IL-1, IL-6, and TNF signaling pathway activation 1

Complications and Organ Involvement

• Coronary artery aneurysms or ectasia develop in 15-25% of untreated children 1
• Systemic inflammation can affect multiple organs 1:
  • Heart (myocarditis, pericarditis, valvulitis)
  • Gastrointestinal tract (abdominal pain, vomiting, diarrhea, gallbladder hydrops)
  • Liver (hepatitis)
  • Lungs (interstitial pneumonitis)
  • Meninges (aseptic meningitis, irritability)
  • Urinary tract (pyuria)
  • Pancreas (pancreatitis)

Key Clinical Pearls and Pitfalls

• Clinical features may not all be present simultaneously; careful history-taking is essential 1
• The diagnosis can be made with fewer than 5 days of fever if typical clinical findings are present 1
• Classic Kawasaki disease can be diagnosed with only 3 clinical features if coronary artery abnormalities are detected on echocardiography 1
• Differential diagnosis must be carefully considered as many conditions can mimic Kawasaki disease 1, 3
• Early treatment (within 10 days of fever onset) significantly reduces the risk of coronary complications 4
• Kawasaki disease should be considered in any child with unexplained fever for 5 or more days 1

Treatment Approach

• Standard initial therapy: intravenous immunoglobulin (IVIG) 2 g/kg as a single infusion with high-dose aspirin 4, 5
• Treatment reduces coronary artery complications from 25% to approximately 5% 4, 6
• 10-15% of patients may be refractory to initial IVIG treatment and require additional therapy 4, 5
• Long-term management depends on the presence and severity of coronary artery abnormalities 2