What are the criteria and indications for Intravenous Immunoglobulin (IVIG) treatment in a pediatric patient under 5 years old with Kawasaki disease?

IVIG Criteria and Indications for Kawasaki Disease in Pediatric Patients Under 5 Years

All children diagnosed with Kawasaki disease should receive IVIG 2 g/kg as a single infusion, regardless of risk stratification scores, because these scoring systems have imperfect predictive value and the priority is preventing coronary artery aneurysms. 1

Classic (Complete) Kawasaki Disease

Treat immediately with IVIG if the child has:

• Fever ≥5 days PLUS
• At least 4 of 5 principal clinical features:
  • Bilateral nonpurulent conjunctivitis
  • Oral mucosal changes (erythema, cracked lips, strawberry tongue)
  • Polymorphous rash
  • Extremity changes (erythema, edema, or desquamation)
  • Cervical lymphadenopathy (≥1.5 cm, usually unilateral) 1, 2, 3

The American Heart Association emphasizes that treatment should be administered within the first 10 days of fever onset, ideally between days 5-10, as this reduces coronary artery aneurysm risk from 25% to less than 5%. 1, 2, 4

Incomplete (Atypical) Kawasaki Disease

This presentation is particularly critical in children under 5 years, especially infants under 1 year, who paradoxically have the highest rates of coronary aneurysms if untreated. 1, 3

Consider incomplete Kawasaki disease and proceed with laboratory testing when:

• Fever ≥5 days PLUS
• Only 2-3 principal clinical features 1

Laboratory criteria supporting treatment:

• CRP ≥3.0 mg/dL and/or ESR elevated
• Additional supportive findings: albumin ≤3.5 g/dL, anemia for age, elevated ALT, platelet count ≥450,000/mm³ after day 7, WBC ≥15,000/mm³, sterile pyuria 1, 2, 3

Echocardiography is mandatory in these cases—if coronary artery abnormalities are present, treat immediately with IVIG even with fewer than 4 clinical criteria. 1, 3

Special Consideration for Infants Under 6 Months

For any infant ≤6 months with:

• Fever ≥7 days
• Laboratory evidence of systemic inflammation
• No alternative explanation for fever

Perform echocardiography and strongly consider IVIG treatment, as young infants frequently present with incomplete disease and have the highest risk of coronary complications. 1

Late Presentation (After Day 10 of Fever)

IVIG should still be administered to children presenting after day 10 if they have:

• Persistent fever without alternative explanation PLUS elevated inflammatory markers (CRP >3.0 mg/dL), OR
• Coronary artery aneurysms with ongoing systemic inflammation 2

The American Heart Association explicitly advises against withholding treatment solely based on timing if inflammation persists—the goal is preventing coronary damage, not adhering rigidly to the day 10 cutoff. 2

Standard Treatment Protocol

Once the decision to treat is made:

• IVIG 2 g/kg as a single infusion over 10-12 hours 2, 3, 5
• High-dose aspirin 80-100 mg/kg/day divided into 4 doses until afebrile for 48-72 hours 2, 3
• Then transition to low-dose aspirin 3-5 mg/kg/day as single daily dose, continuing for 6-8 weeks if no coronary abnormalities develop 2, 3

Critical Pitfalls to Avoid

Common misdiagnoses in children under 5 years:

• Fever with unilateral cervical lymphadenopathy mistaken for bacterial lymphadenitis—the subsequent rash and mucosal changes are then attributed to antibiotic reaction 1
• Sterile pyuria misinterpreted as partially treated UTI 1
• Young infants with fever, rash, and CSF pleocytosis misdiagnosed as viral meningitis 1

Do not wait for all 5 clinical criteria to appear sequentially—they may evolve over days. If 4 criteria are present at any point during the febrile illness, treat immediately. 1

Risk stratification scores (like the Harada score used in Japan) should NOT determine whether to treat in North America—all diagnosed patients receive IVIG because these scores have poor positive predictive value (only 13.8% in boys, 5.5% in girls). 1

Post-Treatment Considerations

Mandatory follow-up requirements:

• Defer measles and varicella immunizations for 11 months after high-dose IVIG 2, 3
• Annual influenza vaccination is required for children on long-term aspirin therapy due to Reye's syndrome risk 2, 3
• Avoid ibuprofen in children taking aspirin as it antagonizes antiplatelet effects 2, 3

IVIG-Resistant Disease (10-20% of Cases)

If fever persists or recurs ≥36 hours after completing initial IVIG:

• First-line: Second dose of IVIG 2 g/kg 2, 3, 6
• Second-line options: IV methylprednisolone 20-30 mg/kg for 3 days OR infliximab 5 mg/kg 2, 3, 6

Frequent echocardiography is essential during the first 3 months, as the highest thrombosis risk occurs during days 15-45. 2, 3