Kawasaki Disease
Self-limited medium-vessel vasculitis of young children; principal threat is coronary artery aneurysms; treated with IVIG and aspirin within 10 days of fever onset.
Also known as: mucocutaneous lymph node syndrome, MCLS, Kawasaki syndrome, infantile polyarteritis
Overview
An acute, self-limited febrile vasculitis of medium-sized arteries that predominantly affects children under 5. Cardinal feature is fever ≥5 days with at least four of: bilateral non-exudative conjunctivitis, oral mucosal changes, extremity changes, polymorphous rash, and unilateral cervical lymphadenopathy. Untreated, 20-25% develop coronary artery aneurysms.
Epidemiology
Highest incidence in children of Asian (especially Japanese) descent; ~6,000 US cases/year. 80% of cases in children <5 years. Slight male predominance. Peak in late winter and spring. Etiology unknown, presumed infectious trigger in a genetically predisposed host.
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Risk factors
- Age <5 years
- Asian (especially Japanese, Korean) ancestry
- Male sex
- Sibling with prior Kawasaki disease
- MIS-C following SARS-CoV-2 has overlapping features but is a distinct entity
Pathophysiology
Postulated infectious trigger initiates an immune cascade in genetically susceptible children, leading to medium-vessel vasculitis with prominent coronary artery involvement. Activated T cells, macrophages, and cytokine surge produce endothelial dysfunction and arterial wall edema, weakening and dilating affected vessels.
Clinical presentation
Symptoms
- Fever ≥5 days, often 39-40 °C, unresponsive to antipyretics
- Bilateral non-exudative conjunctival injection with limbic sparing
- Lip changes: red, dry, cracked, fissured; strawberry tongue
- Extremity changes: erythema and edema of palms and soles in week 1; periungual desquamation in week 2-3
- Polymorphous rash: morbilliform, scarlatiniform, or erythema multiforme-like; perineal accentuation in infants
- Unilateral cervical lymphadenopathy ≥1.5 cm
- Irritability disproportionate to exam, especially infants
Signs / physical exam
- Tachycardia disproportionate to fever
- BCG site reactivation (red, indurated) where BCG given
- Hydrops of gallbladder, sterile pyuria, arthritis, aseptic meningitis can occur
Classic findings
Cracked red lips, strawberry tongue, red palms and soles, bilateral conjunctivitis, and a polymorphous rash in a febrile irritable toddler.
Differential diagnosis
- Scarlet fever — Strep pharyngitis with sandpaper rash; lacks extremity changes and conjunctivitis
- Measles — Three Cs and Koplik spots; cephalocaudal rash
- Stevens-Johnson syndrome — Mucosal involvement with sloughing and target lesions, drug exposure
- Staphylococcal or streptococcal toxic shock — Hypotension and end-organ failure; toxin-mediated
- Multisystem inflammatory syndrome in children (MIS-C) — Recent SARS-CoV-2 exposure, older children, more cardiac dysfunction and shock; overlaps significantly with Kawasaki
- Juvenile idiopathic arthritis (systemic) — Quotidian fevers, salmon rash, arthritis; ferritin extremely high
- Adenovirus — Exudative conjunctivitis (vs non-exudative in KD); shorter fever course
Diagnostic workup
Diagnostic criteria
Classic Kawasaki: fever ≥5 days plus ≥4 of 5 principal features (conjunctivitis, lip/oral changes, extremity changes, rash, cervical adenopathy). Incomplete Kawasaki: fever ≥5 days with 2-3 features plus supportive labs and/or coronary changes.
Labs
- CBC: leukocytosis with left shift in week 1, thrombocytosis (>450,000) classically appears in week 2
- ESR and CRP elevated; persistent elevation supports diagnosis
- LFTs: mild transaminitis, hypoalbuminemia
- Urinalysis: sterile pyuria
- BNP/NT-proBNP often elevated
- Echocardiogram at diagnosis, 1-2 weeks, and 4-6 weeks — assess coronary artery dimensions (z-scores)
- Consider SARS-CoV-2 testing (PCR and antibody) to distinguish from MIS-C in current era
Imaging
- Transthoracic echocardiogram is mandatory and serial
- ECG to detect arrhythmias and ischemia
- Cardiac MRI or coronary CT for follow-up of aneurysms
Diagnostic algorithm
flowchart TD
A[Fever ≥5 days<br/>young child] --> B{≥4 of 5 features?<br/>conj / lips / extremities<br/>rash / cervical node}
B -->|Yes| C[Classic Kawasaki]
B -->|2-3 features| D[Incomplete Kawasaki<br/>check CRP/ESR + echo]
D -->|Supportive| C
C --> E[IVIG 2 g/kg + high-dose ASA<br/>within 10 days]
E --> F{Fever resolves<br/>≤36 h?}
F -->|Yes| G[Low-dose ASA<br/>+ serial echo]
F -->|No| H[IVIG-resistant:<br/>repeat IVIG ± steroids<br/>± infliximab]
G --> I{Coronary aneurysm?}
I -->|Small| J[Continue low-dose ASA]
I -->|Large/giant| K[ASA + anticoagulation<br/>lifelong cardiology follow-up]Treatment
First-line
- IVIG + ASA for Kawasaki — IVIG 2 g/kg as a single infusion over 10-12 hours within 10 days of fever onset (and ideally before day 7)
- High-dose aspirin 30-50 mg/kg/day in 4 divided doses until afebrile for 48-72 hours, then low-dose aspirin 3-5 mg/kg/day until inflammatory markers and coronary imaging normalize
- Continue low-dose aspirin if coronary aneurysms develop; add anticoagulation (warfarin, LMWH) for large or giant aneurysms
IVIG-resistant Kawasaki
- Persistent or recurrent fever ≥36 hours after IVIG
- Re-treat with second IVIG 2 g/kg
- Adjunctive corticosteroids (methylprednisolone pulse or prednisolone taper) for high-risk patients (Kobayashi score)
- Infliximab or cyclosporine as third-line
Late presentation (>10 days)
- Treat with IVIG if persistent fever, ongoing inflammation, or coronary changes
- Aspirin and serial echocardiography
Second-line / adjunct
- Live vaccines (MMR, varicella) should be delayed 11 months after IVIG (passive antibody interferes with the live-vaccine immune response); inactivated influenza vaccine is unaffected and need not be deferred
- Avoid live MMR/varicella for 11 months after IVIG
Complications
- Coronary artery aneurysms (giant aneurysm = z-score >10 or >8 mm) with risk of thrombosis, stenosis, MI, and sudden death
- Myocarditis, pericarditis, valvular regurgitation
- Arrhythmias
- Long-term: premature atherosclerosis, even without persistent aneurysm
- Hepatitis, gallbladder hydrops, sterile pyuria, aseptic meningitis (typically self-limited)
PANCE pearls
- Fever ≥5 days with at least four principal features — start IVIG within 10 days to reduce aneurysm rate from 20-25% to ~3-5%.
- Periungual desquamation in week 2-3 is a retrospective clue but cannot wait — diagnose and treat early on fever and other features.
- Aspirin is one of the few pediatric indications that overrides Reye-syndrome avoidance; benefits outweigh risks here.
- Defer live vaccines (MMR, varicella) for 11 months after IVIG.
- Incomplete Kawasaki is more common in infants and requires supportive labs plus echo to support diagnosis.
References
- AHA 2017 — AHA Scientific Statement: Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease (McCrindle et al., Circulation 2017;135:e927-e999)
- AAP Red Book — American Academy of Pediatrics Red Book — Kawasaki Disease
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