The diagnosis is Kawasaki disease.
1. Definition
Kawasaki disease (KD) is an acute, self-limited systemic vasculitis of predominantly medium-sized arteries that primarily affects young children and has a particular predilection for the coronary arteries.
It is a major cause of acquired heart disease in children in developed countries.
2. Etiology
1. Exact cause is unknown
2. Likely results from an abnormal immune response to environmental or infectious triggers in genetically susceptible children
3. Causes widespread vascular inflammation with prominent involvement of the coronary arteries
3. Pathophysiology
1. Immune activation produces systemic inflammation and cytokine release
2. Inflammation involves medium-sized arteries, particularly the coronary arteries
3. Coronary arteritis damages the arterial wall
4. Vessel-wall weakening can produce coronary artery dilation and aneurysms
5. Large or giant aneurysms predispose to:
o Coronary thrombosis
o Stenosis
o Myocardial ischemia or infarction
4. Clinical Features
4.1 Complete Kawasaki Disease
Complete Kawasaki disease is diagnosed in a child with fever for at least 4 days plus at least 4 of the 5 principal clinical features, provided there is no better alternative diagnosis.
The clinical features may appear sequentially and do not need to be present simultaneously.
The five principal features are:
1. Bilateral conjunctival injection
o Typically nonexudative
2. Polymorphous rash
o Usually nonvesicular
3. Cervical lymphadenopathy
o Usually unilateral
o At least one lymph node typically ≥1.5 cm
4. Oral mucosal changes
o Strawberry tongue
o Red, cracked lips
o Diffuse oral or pharyngeal erythema
5. Extremity changes
o Acute phase: erythema and edema of the hands and feet
o Subacute phase: periungual desquamation
4.2 Incomplete Kawasaki Disease
1. Should be considered in children with prolonged unexplained fever who have fewer than four principal clinical features
2. Diagnosis is supported by:
o Elevated inflammatory markers
o Compatible laboratory abnormalities
o Coronary artery abnormalities on echocardiography
3. Treatment should not be delayed when incomplete KD is strongly suspected
4.3 Additional Features
1. Marked irritability
2. Gastrointestinal symptoms
3. Arthritis or arthralgia
4. Sterile pyuria
5. Elevated liver enzymes
6. Hypoalbuminemia
7. Perineal erythema or desquamation
5. Diagnosis
Kawasaki disease is primarily a clinical diagnosis. There is no single pathognomonic laboratory test.
5.1 Laboratory Findings
Common supportive findings include:
1. Elevated CRP and ESR
2. Leukocytosis
3. Normocytic anemia
4. Thrombocytosis, typically developing during the second week or subacute phase
5. Possible:
o Hypoalbuminemia
o Elevated ALT
o Sterile pyuria
5.2 Echocardiography
1. Echocardiography should be performed when KD is diagnosed or strongly suspected
2. It assesses:
o Coronary artery dilation or aneurysms
o Ventricular function
o Myocarditis
o Pericardial effusion
o Valvular dysfunction
3. Coronary artery dimensions should be interpreted using body-surface-area-adjusted Z scores
4. A normal early echocardiogram does not exclude Kawasaki disease
5.3 Coronary Artery Classification
Coronary abnormalities are classified primarily using Z scores:
1. No involvement: Z score <2
2. Dilation only: Z score 2 to <2.5
3. Small aneurysm: Z score ≥2.5 to <5
4. Medium aneurysm: Z score ≥5 to <10
5. Large or giant aneurysm: Z score ≥10
6. Absolute coronary artery dimensions should also be considered during specialist risk assessment
6. Management
6.1 Intravenous Immunoglobulin
1. IVIG 2 g/kg as a single infusion is standard initial therapy
2. Treatment should be given as soon as the diagnosis is established, ideally within the first 10 days of illness
3. Patients presenting after day 10 may still require IVIG if there is:
o Persistent fever
o Ongoing systemic inflammation
o Coronary artery aneurysm
4. IVIG substantially reduces the risk of developing coronary artery abnormalities
6.2 Aspirin
1. During the acute febrile phase:
o Aspirin 30 to 50 mg/kg/day orally, divided every 6 hours
2. Once afebrile for approximately 48 to 72 hours:
o Transition to low-dose aspirin 3 to 5 mg/kg once daily
3. Duration of low-dose aspirin depends on the presence and severity of coronary artery involvement
6.3 High-Risk Disease
1. High-risk features include:
o Age ≤6 months
o Left anterior descending coronary artery or right coronary artery Z score ≥2.5 on the baseline echocardiogram
2. High-risk patients may benefit from intensified initial anti-inflammatory therapy, commonly IVIG plus adjunctive corticosteroid therapy in appropriate patients
3. Management should involve pediatric cardiology and clinicians experienced in Kawasaki disease
6.4 Management of Coronary Aneurysms
Antithrombotic therapy is based on aneurysm size and persistence:
1. Small aneurysm
o Low-dose aspirin
2. Medium aneurysm, current or persistent
o Low-dose aspirin plus clopidogrel
o Routine systemic anticoagulation is not indicated
3. Large or giant aneurysm, current or persistent
o Low-dose aspirin
o Systemic anticoagulation with warfarin, low-molecular-weight heparin, or an appropriate direct oral anticoagulant under specialist supervision
o Additional clopidogrel may be considered in selected patients
4. Long-term pediatric cardiology surveillance is required for persistent coronary aneurysms
6.5 IVIG-Resistant Kawasaki Disease
1. IVIG resistance is defined by persistent or recrudescent fever ≥38°C at least 36 hours after completion of the initial IVIG infusion
2. Additional treatment may include:
o Repeat IVIG
o Corticosteroids
o Other anti-inflammatory therapies in selected refractory cases
7. Complications
7.1 Cardiovascular Complications
1. Coronary artery aneurysms, the most important complication
2. Coronary artery thrombosis
3. Coronary stenosis
4. Myocardial infarction
5. Myocarditis
6. Ventricular dysfunction
7. Pericarditis
8. Valvular dysfunction
Large or giant coronary aneurysms carry the greatest long-term risk of thrombosis and myocardial ischemia.
8. Key Clinical Insight
A child with prolonged fever, bilateral nonexudative conjunctival injection, oral mucosal changes, polymorphous rash, extremity changes, cervical lymphadenopathy, and coronary artery aneurysms has a classic presentation of Kawasaki disease. Prompt IVIG therapy is essential to reduce further coronary artery injury.
References
1. Jone PN, Tremoulet A, Choueiter N, et al. Update on Diagnosis and Management of Kawasaki Disease: A Scientific Statement From the American Heart Association. Circulation. 2024;150(23):e481-e500. doi:10.1161/CIR.0000000000001295.
2. Gorelik M, Chung SA, Ardalan K, et al. 2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Kawasaki Disease. Arthritis Rheumatol. 2022;74(4):586-596. doi:10.1002/art.42041.
3. Jone PN, Tremoulet A, Choueiter N, et al. Correction to: Update on Diagnosis and Management of Kawasaki Disease: A Scientific Statement From the American Heart Association. Circulation. 2025;151:e677-e679. doi:10.1161/CIR.0000000000001313.
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