Definition
Kawasaki Disease (KD) is an acute, self-limited vasculitis that predominantly affects small to medium-sized arteries, with a particular predilection for the coronary arteries. Although its exact etiology remains unknown, it is believed to involve abnormal immune activation in genetically predisposed children, likely triggered by infectious agents.
✅ KD is the leading cause of acquired heart disease in children in developed countries.
Epidemiology
- Age: Primarily affects children 6 months to 5 years old; rare in infants <3 months and children >7 years.
- Gender: More common in males (M:F ratio ~1.5:1).
- Ethnicity:
- Asian (particularly Japanese and Korean) children are at the highest risk.
- Afro-Caribbean populations also show increased susceptibility.
- Incidence:
- Japan: ~300 per 100,000 children under 5
- USA/Europe: ~10–25 per 100,000 children under 5
Clinical Features
Classic (Complete) Kawasaki Disease
Diagnosis requires:
- Fever ≥5 days plus at least 4 of the 5 following features (in the absence of another explanation):
| Clinical Feature | Description |
|---|---|
| Conjunctivitis | Bilateral, non-purulent bulbar conjunctival injection (no exudate) |
| Oral changes | Erythematous lips, strawberry tongue, red pharynx |
| Peripheral changes | Erythema and edema of hands/feet in acute phase; periungual desquamation in subacute phase (10–15 days after onset) |
| Rash | Polymorphous, non-vesicular; may involve trunk, extremities, perineum |
| Cervical lymphadenopathy | ≥1 lymph node >1.5 cm, typically unilateral |
⚠️ Incomplete (atypical) KD should be suspected in infants <6 months with persistent unexplained fever, especially with elevated inflammatory markers and coronary artery changes.
Differential Diagnoses
- Measles
- Adenovirus
- Epstein-Barr virus (EBV)
- Group A Streptococcal infection (scarlet fever)
- Systemic juvenile idiopathic arthritis
- Multisystem inflammatory syndrome in children (MIS-C)
Coronary Artery Involvement
- Aneurysm formation can occur in 15–25% of untreated patients.
- Risk drops to <5% with early IVIg therapy.
- Aneurysms are most commonly detected 7–14 days after symptom onset.
- Giant aneurysms (>8 mm) carry the highest risk of thrombotic complications.
Risk Stratification: Kobayashi Score
Used mainly in Japanese populations to predict IVIg resistance and coronary involvement.
| Criterion | Points |
|---|---|
| Sodium <133 mmol/L | 2 |
| Illness duration ≤4 days | 2 |
| Neutrophils ≥80% | 2 |
| ALT >100 IU/L | 1 |
| Platelet count <300,000/µL | 1 |
| CRP >100 mg/L | 1 |
| Age <12 months | 1 |
Score ≥5 suggests higher risk and may prompt early adjunctive therapy (e.g., corticosteroids).
Investigations
Initial Laboratory Workup
- CBC:
- Early: Neutrophilia, normocytic anemia, possible thrombocytopenia
- Subacute: Reactive thrombocytosis
- Inflammatory markers: Elevated ESR and CRP
- LFTs: Raised ALT, AST, and bilirubin; low albumin
- Urinalysis: Sterile pyuria common
- Throat swab, ASO titer, measles/EBV PCR: To rule out other causes
- Blood culture: To exclude sepsis
Cardiac Assessment
- Echocardiogram: Essential to detect coronary artery dilatation/aneurysm
- Baseline, at 2 weeks, and at 6 weeks
- ECG: May reveal heart block or myocarditis
Other Considerations
- CSF study: If signs of meningitis
- NT-proBNP and troponin: To evaluate for myocardial involvement
Management
1. Intravenous Immunoglobulin (IVIg)
- Dose: 2 g/kg IV over 10–12 hours
- Should be administered ideally within the first 10 days of illness (as early as possible)
- Reduces risk of coronary aneurysms
2. Aspirin
- High-dose (anti-inflammatory): 30–50 mg/kg/day (divided QID) until afebrile for 48–72 hrs
- Then switch to low-dose (antiplatelet): 3–5 mg/kg/day until coronary status confirmed
Aspirin should be continued until 6–8 weeks, or longer if coronary changes persist.
3. Adjunctive Therapy (High-risk or IVIg-resistant cases)
- Methylprednisolone IV (30 mg/kg for 1–3 days) or oral prednisolone 2 mg/kg/day tapered over 2–3 weeks
- Second dose of IVIg
- Infliximab (anti-TNF) or anakinra (IL-1 inhibitor) for refractory cases
Discharge and Follow-Up
- Ensure patient is afebrile and inflammatory markers declining before discharge
- Continue echocardiographic monitoring at:
- 2 weeks
- 6 weeks
- 6 months (if coronary abnormalities persist)
| Coronary Findings | Management |
|---|---|
| No aneurysms at 6 weeks | Stop aspirin, resume normal activities |
| Aneurysm <8 mm | Continue aspirin 2–5 mg/kg/day until resolution |
| Multiple or giant aneurysms (≥8 mm) | Lifelong low-dose aspirin + cardiology follow-up (± anticoagulation) |
Key Points for Medical Students
- Always consider KD in a febrile child with rash and mucocutaneous signs, especially if the fever lasts ≥5 days.
- Prompt treatment with IVIg reduces risk of serious cardiac sequelae.
- Not all KD cases meet classic criteria — incomplete presentations are common, especially in infants.
- Kawasaki Disease is clinical diagnosis, supported by investigations to exclude other causes and assess complications.
- Do not delay treatment while waiting for echo if clinical suspicion is high.
Further Reading
- McCrindle BW et al. “Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease.” Circulation. 2022;145(3):e1–e16.
- AHA Guidelines for Kawasaki Disease – 2022 Update
- RCPCH UK Clinical Practice Guidance on Kawasaki and PIMS (2023)
