What is the appropriate management and treatment for a young child under the age of 5 diagnosed with Kawasaki disease?

Management and Treatment of Kawasaki Disease in Young Children

All children under age 5 diagnosed with Kawasaki disease should be treated immediately with intravenous immunoglobulin (IVIG) 2 g/kg as a single infusion over 10-12 hours combined with high-dose aspirin 80-100 mg/kg/day divided into four doses, initiated as early as possible within the first 10 days of fever onset. 1, 2

Diagnostic Confirmation Before Treatment

• Classic Kawasaki disease requires fever lasting at least 5 days plus at least 4 of 5 principal features: bilateral non-purulent conjunctival injection, oral mucosal changes (cracked lips, strawberry tongue), polymorphous rash, extremity changes (erythema/edema of hands and feet), and cervical lymphadenopathy ≥1.5 cm. 1, 3

• Infants under 6 months are at highest risk for incomplete presentations and paradoxically have the highest rates of coronary aneurysms if untreated, so maintain high clinical suspicion even with atypical presentations. 2, 3

• For incomplete Kawasaki disease (fever ≥5 days with only 2-3 principal features), check inflammatory markers (ESR, CRP) and perform echocardiography; treat if CRP >3.0 mg/dL or coronary abnormalities are present. 1, 4

• Diagnosis can be made on day 4 of fever if 4 principal criteria are present, allowing earlier treatment initiation. 1, 4

Acute Phase Treatment Protocol

The cornerstone of treatment is IVIG 2 g/kg as a single infusion, which reduces coronary artery abnormality risk from 15-25% down to approximately 5% for any abnormality and 1% for giant aneurysms. 1, 2, 3

Initial Therapy Regimen:

• IVIG 2 g/kg as single infusion over 10-12 hours 1, 2
• High-dose aspirin 80-100 mg/kg/day divided into four doses during acute phase 1, 2
• Continue high-dose aspirin until patient has been afebrile for 48-72 hours 1, 2
• Then transition to low-dose aspirin 3-5 mg/kg/day as single daily dose 1, 2

Timing Considerations:

• Treat as soon as diagnosis is established, ideally within first 10 days of fever onset 1, 2
• Children presenting after day 10 should still receive IVIG if they have ongoing systemic inflammation (elevated ESR or CRP >3.0 mg/dL) or coronary abnormalities 1
• Those presenting late without fever, normalized labs, and normal echocardiograms do not require IVIG 1

Management of IVIG-Resistant Disease

IVIG resistance occurs in 10-20% of patients, defined as persistent or recrudescent fever ≥36 hours after completing initial IVIG infusion. 2

Second-Line Treatment Options:

• Administer second dose of IVIG 2 g/kg as single infusion 1, 2
• Alternative options include methylprednisolone 20-30 mg/kg IV for 3 days or infliximab 5 mg/kg IV over 2 hours as single infusion 2

Aspirin Dosing Algorithm and Duration

Acute Phase:

• High-dose aspirin 80-100 mg/kg/day in four divided doses until afebrile for 48-72 hours 1, 2

Convalescent Phase (No Coronary Abnormalities):

• Low-dose aspirin 3-5 mg/kg/day as single dose 1, 2
• Continue until 6-8 weeks after disease onset 1, 2
• Then discontinue if echocardiogram remains normal 2

Long-Term Antiplatelet Therapy (With Coronary Abnormalities):

• Small aneurysms: Low-dose aspirin 3-5 mg/kg/day indefinitely 2
• Moderate aneurysms: Low-dose aspirin 3-5 mg/kg/day plus clopidogrel 1 mg/kg/day (max 75 mg/day) 2
• Giant aneurysms: Low-dose aspirin 3-5 mg/kg/day plus warfarin with target INR 2.0-3.0 2

Cardiac Monitoring Protocol

• Perform echocardiography at diagnosis, 2 weeks, and 6-8 weeks after treatment initiation 2
• Frequent echocardiography and ECG during first 3 months after diagnosis, especially for giant aneurysms 2
• CRP is more accurate than ESR for monitoring inflammation after IVIG therapy, as IVIG artificially elevates ESR 2
• Risk stratification for long-term management is based on maximal coronary artery luminal dimensions normalized as Z scores 3

Critical Pitfalls and Caveats to Avoid

Never use ibuprofen in children taking aspirin for antiplatelet effects, as it antagonizes the irreversible platelet inhibition induced by aspirin. 2

• Children may present with only fever and unilateral cervical lymphadenopathy, with rash and mucosal changes mistaken for antibiotic reaction; maintain high suspicion for Kawasaki disease. 1

• Sterile pyuria may be mistaken for partially treated urinary tract infection; consider Kawasaki disease in differential. 1

• Young infants may present with fever, rash, and CSF pleocytosis mimicking viral meningitis. 1

• Annual influenza vaccination is mandatory for children on long-term aspirin therapy due to Reye syndrome risk during influenza infection. 1, 2

• Defer measles, mumps, rubella, and varicella immunizations for 11 months after high-dose IVIG administration due to interference with vaccine efficacy. 2

• Older children and adolescents often have delayed diagnosis and higher prevalence of coronary artery abnormalities. 4

• All patients diagnosed with Kawasaki disease should be treated with IVIG regardless of risk scores, as scoring systems have imperfect performance. 1