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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.
Classic KD: Fever ≥5 days + ≥4 of 5 features [conjunctival injection, oral changes, rash, extremity changes, cervical lymphadenopathy]; Incomplete KD: Fever ≥5 days + <4 features + CRP ≥3mg/dL or ESR ≥40mm/hr + ≥3 supplemental lab criteria OR echocardiographic evidence of CAA; Treatment: IVIG 2g/kg single infusion + Aspirin 30-50mg/kg/day (acute phase)
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
IVIG 2g/kg over 12 hours + aspirin 30-50mg/kg/day in 4 divided doses; echo at diagnosis
This child meets classic criteria with all 5 principal features. Treatment must not be delayed. Echo will assess baseline coronary artery dimensions for Z-score calculation.
Z-score ≥2.5 on echo is diagnostic criterion for incomplete KD; treat with IVIG + aspirin
Incomplete KD is particularly common in infants under 6 months who may lack classic features but are at highest risk of coronary aneurysm. Echo is essential and often makes the diagnosis.
Cardiology input essential; long-term follow-up for potential stenosis and MI risk
Giant aneurysms (Z-score ≥10) have the highest risk of thrombosis and myocardial infarction. Dual antiplatelet therapy or anticoagulation is required alongside aspirin, and coronary intervention may be needed in adulthood.
Repeat echo before second treatment; higher risk of coronary involvement in resistant cases
IVIG resistance occurs in 10-20% of KD. Infliximab (anti-TNF) has been shown to produce faster defervescence than second IVIG and may be preferred for those with coronary abnormalities at presentation.
Paediatric emergency and inpatient assessment of children with unexplained prolonged fever and mucocutaneous signs.
Echocardiographic surveillance in treated KD patients — coronary artery Z-scores guide treatment duration and intensity.
Paediatric rheumatology and cardiology follow-up for children with persistent or giant coronary aneurysms.
Distinction from MIS-C in post-COVID era — KD criteria assessment alongside COVID serology guides appropriate treatment pathway.
Public health epidemiology: national and international KD registries track incidence trends, treatment outcomes, and search for aetiological clues.
Kawasaki Disease in Infants Under 6 Months
Infants under 6 months of age are at highest risk for coronary aneurysm and are most likely to present with incomplete KD (fewer than 4 principal features). Any infant under 6 months with fever for 7 or more days without an identified source should have an echocardiogram to exclude KD. A low threshold for treatment is recommended in this age group.
MIS-C (Multisystem Inflammatory Syndrome in Children)
SARS-CoV-2 infection can trigger Multisystem Inflammatory Syndrome in Children (MIS-C), which shares features with Kawasaki disease including fever, mucocutaneous changes, and coronary artery involvement. MIS-C typically presents 2-6 weeks after COVID infection, tends to affect older children, causes more myocarditis and shock, and requires a different management approach. The conditions overlap but are distinct.
IVIG Resistance Prediction
Several Japanese scoring systems (Egami, Kobayashi, Sano) predict IVIG resistance before treatment, allowing identification of high-risk patients who may benefit from initial combination therapy (IVIG + corticosteroids or infliximab). These scores incorporate laboratory values (sodium, CRP, AST, total bilirubin) and age. They are less validated in non-Japanese populations.
Macrophage Activation Syndrome (MAS) in KD
Macrophage activation syndrome is a rare but life-threatening complication of KD characterised by cytopenias, hyperferritinaemia, hepatosplenomegaly, and coagulopathy. It requires immediate recognition and treatment with high-dose corticosteroids or biologics. Persistent fever, worsening liver function, and falling platelet count in a child with KD should raise this possibility.
| Z-Score | Classification | Treatment Addition | Follow-Up |
|---|---|---|---|
| <2 | Normal | Aspirin alone (short-term) | Echo at diagnosis, 2 weeks, 6-8 weeks then discharge |
| 2-2.5 | Dilation | Aspirin | Echo at 1-2 week intervals until normalised |
| 2.5-5 | Small aneurysm | Aspirin ± antiplatelet | Cardiology follow-up; echo 3-monthly |
| 5-10 | Medium aneurysm | Aspirin + antiplatelet | Cardiac MRI; annual stress testing |
| ≥10 | Giant aneurysm | Aspirin + anticoagulation (warfarin/LMWH) | Lifelong cardiology; coronary angiography; possible PCI/CABG |
What causes Kawasaki disease?
The exact cause remains unknown despite decades of research. An infectious trigger (possibly a respiratory pathogen) in genetically predisposed individuals is the leading hypothesis. Proposed triggers include coronaviruses, bocavirus, and various bacteria. The seasonal clustering of cases in winter-spring and the epidemic pattern in some regions support an infectious aetiology, but no single causative agent has been consistently identified.
How long after fever onset should IVIG be given?
IVIG is most effective when given between days 5 and 10 of fever onset, reducing coronary aneurysm risk from ~25% to <5%. IVIG given before day 4 may be less effective due to incomplete immune activation. IVIG given after day 10 should still be administered if there is evidence of ongoing inflammation (elevated CRP/ESR) or if coronary abnormalities are already present.
What dose of aspirin is used in Kawasaki disease?
In the acute phase, aspirin is used at anti-inflammatory doses: 30-50 mg/kg/day in 4 divided doses (some centres use 80-100 mg/kg/day). Once the child is afebrile for 48-72 hours, aspirin is stepped down to antiplatelet doses: 3-5 mg/kg/day once daily. Children without coronary abnormalities can usually stop aspirin after 6-8 weeks; those with aneurysms continue indefinitely.
What are coronary artery Z-scores?
Z-scores normalise coronary artery internal diameter measurements for body surface area, allowing comparison across children of different sizes. A Z-score of 0 is the population mean, ±2 represents 2 standard deviations. In KD: normal <2; dilation 2-2.5; small aneurysm 2.5-5; medium 5-10; giant ≥10. Z-scores guide treatment intensity and long-term follow-up planning.
Can adults get Kawasaki disease?
Kawasaki disease is extremely rare in adults (>18 years) and the diagnosis is easily confused with other febrile illnesses. When it does occur in adults, it is often severe with high rates of coronary involvement. Many adults presenting with unexplained myocardial infarction and no traditional risk factors are subsequently found to have coronary aneurysms consistent with unrecognised childhood KD.
Why is periungual desquamation important in KD?
Periungual desquamation (peeling of the skin around the fingernails and toenails) is a highly characteristic feature of KD that typically appears 2-3 weeks after the onset of fever, in the subacute phase. It should not be waited for before initiating treatment but, when present retrospectively, it strongly supports a diagnosis of KD in a child who had an unexplained febrile illness.
Is Kawasaki disease more common in certain ethnicities?
Yes. The highest incidence is in Japan (approximately 330 per 100,000 children under 5 per year) and other East Asian countries (Korea, Taiwan). In Western countries, Asian children have 5-10 times higher incidence than Caucasian children. However, KD occurs in all ethnicities and must be considered in any child of any background with unexplained prolonged fever and mucocutaneous features.
What is the long-term outlook for children with Kawasaki disease?
Children without coronary artery involvement have normal long-term outcomes and are considered cured after 6-8 weeks. Children with persistent small aneurysms may see regression over 1-2 years but require ongoing cardiology follow-up. Those with giant aneurysms are at lifelong risk of coronary artery stenosis, myocardial infarction, and sudden death, requiring anticoagulation, regular imaging, and possible coronary intervention.
Pro Tip
In any child with unexplained fever lasting more than 5 days, especially under age 5, perform a systematic review of all 5 Kawasaki criteria at every clinical assessment. Missing even one feature (e.g., perineal or periungual rash) can prevent timely diagnosis. Document the specific character of each mucocutaneous feature — 'rash' is insufficient; note morphology, distribution, and timing.
Did you know?
Kawasaki disease was first described in 1967 by Dr Tomisaku Kawasaki, a Japanese paediatrician, who observed 50 children with a distinctive febrile illness at the Red Cross Hospital in Tokyo. He initially called it 'mucocutaneous lymph node syndrome'. The link to coronary artery aneurysms was not recognised for several more years, as early cases were only identified at autopsy. Dr Kawasaki, who lived to age 95, always maintained that the cause of the disease bearing his name would eventually be found — it has not yet been definitively identified.
References
- ›McCrindle BW et al. Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease. Circulation 2017 (AHA Scientific Statement).
- ›Kawasaki T. Acute febrile mucocutaneous syndrome with lymphoid involvement with specific desquamation of the fingers and toes in children. Allergy 1967 (English translation).
- ›NICE Guideline NG143 — Fever in under 5s: assessment and initial management. 2019.
- ›Newburger JW et al. Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease. Circulation 2004.
- ›Printz BF et al. Noncoronary cardiac abnormalities are associated with coronary artery dilation in Kawasaki disease. J Am Coll Cardiol 2011.
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