Kawasaki Disease Diagnostic Criteria

Kawasaki disease (KD) is an acute, self-limiting systemic vasculitis of unknown aetiology that predominantly affects children under 5 years of age, particularly those of East Asian descent, though it occurs in all ethnic groups worldwide. It is now the most common cause of acquired heart disease in children in developed countries, having largely replaced rheumatic fever in this role. The primary concern with Kawasaki disease is the development of coronary artery aneurysms (CAAs), which occur in up to 25% of untreated patients but are reduced to less than 5% with timely treatment. Classic Kawasaki disease is diagnosed clinically by the presence of fever lasting 5 or more days plus at least 4 of 5 principal features: bilateral non-purulent conjunctival injection, oral changes (strawberry tongue, red cracked lips, pharyngeal erythema), polymorphous rash, extremity changes (erythema and oedema of hands and feet in the acute phase, periungual desquamation in the subacute phase), and cervical lymphadenopathy (unilateral, ≥1.5 cm). Incomplete or atypical Kawasaki disease, presenting with fever for 5 or more days and fewer than 4 principal features, requires laboratory criteria and echocardiography for diagnosis and carries the same risk of coronary aneurysms. Treatment consists of intravenous immunoglobulin (IVIG) 2 g/kg as a single infusion plus aspirin, which together reduce CAA risk dramatically when given within 10 days of fever onset. Aspirin is used at anti-inflammatory doses acutely then switched to antiplatelet doses once the child is afebrile. Echocardiography is essential for all suspected cases at diagnosis and serially thereafter.

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1. 1Document fever duration precisely: fever must be present for ≥5 days (or fewer if clinical features are compelling and senior clinician diagnosis is made). Record daily temperature charts.
2. 2Systematically assess each of the 5 principal features: (1) bilateral non-purulent conjunctival injection without discharge or periorbital oedema; (2) oral changes — strawberry tongue, red/cracked lips, diffuse pharyngeal erythema; (3) polymorphous rash (maculopapular, diffuse erythroderma, or targetoid — any morphology); (4) extremity changes — oedema or erythema of palms/soles, or periungual desquamation (appears 2-3 weeks after fever onset); (5) unilateral anterior cervical lymphadenopathy ≥1.5 cm.
3. 3If classic criteria are not met (fewer than 4 features), assess for incomplete KD: obtain CRP and ESR. If CRP ≥3 mg/dL or ESR ≥40 mm/hr, check supplemental laboratory criteria: albumin ≤3 g/dL, anaemia for age, ALT elevated, platelet count ≥450,000 after day 7, WBC ≥15,000, urine ≥10 WBCs per high-power field. Three or more supplemental criteria support the diagnosis of incomplete KD.
4. 4Perform echocardiography in all suspected cases: coronary artery dilation or aneurysm (Z-score ≥2.5) is diagnostic of KD in incomplete cases and guides treatment decisions throughout management.
5. 5Classify coronary artery involvement using Z-scores: normal <2; dilation 2-2.5; small aneurysm 2.5-5; medium aneurysm 5-10; giant aneurysm ≥10. Giant aneurysms carry the highest thrombotic risk and long-term cardiovascular morbidity.
6. 6Initiate treatment as soon as diagnosis is established or strongly suspected: IVIG 2 g/kg IV over 12 hours plus aspirin. For 'classic' KD, treatment should not wait for echo results.
7. 7Monitor for IVIG resistance (defined as persistent or recrudescent fever ≥36 hours after IVIG completion): approximately 10-20% of cases require a second IVIG dose or infliximab therapy. Steroid therapy (prednisolone) is also used in resistant cases in some guidelines.

• !Waiting for all 5 classic features before considering diagnosis — incomplete KD is common and carries equal coronary risk; 4 features with fever ≥5 days is sufficient for classic KD.
• !Diagnosing KD before 5 days of fever in non-urgent situations — early treatment before day 4 may be less effective and risks over-diagnosis.
• !Not performing echocardiography at diagnosis — coronary artery dimensions are essential baseline data for all suspected KD cases.
• !Using only the total platelet count to exclude KD — thrombocytosis (>450,000) typically develops in the second week; normal platelets in the first week do not exclude the diagnosis.
• !Stopping aspirin after IVIG without confirming the child is afebrile for 48-72 hours and CRP is trending down.
• !Not following up coronary artery Z-scores over time — aneurysms may regress or progress, and management changes accordingly.