Overview
Definition:
Kawasaki disease (KD) is an acute febrile vasculitis of unknown etiology affecting medium-sized arteries, most notably the coronary arteries
It is the leading cause of acquired heart disease in children in developed countries
Coronary artery abnormalities (CAA), including aneurysms, are the most serious complication.
Epidemiology:
Primarily affects children younger than 5 years
Incidence varies geographically, with higher rates in East Asian populations
Most cases occur during winter and spring
Recurrence is uncommon but possible.
Clinical Significance:
The primary concern in KD is the development of coronary artery aneurysms, which can lead to myocardial infarction, sudden death, or arrhythmias in later life
Timely diagnosis and appropriate management, including intravenous immunoglobulin (IVIG) and aspirin, are crucial to reduce the risk of CAA
Long-term surveillance is essential for affected individuals.
Clinical Presentation
Symptoms:
Fever lasting at least 5 days
Bilateral non-exudative conjunctivitis
Oral mucosal changes: dry, cracked lips
strawberry tongue
diffuse erythema of oral mucosa
Polymorphous rash, typically truncal
Cervical lymphadenopathy (>1.5 cm, unilateral)
Extremity changes: erythema and edema of hands and feet, followed by desquamation.
Signs:
Fever >38.5°C
Conjunctival injection
Redness of lips and oral mucosa
Rash morphology varies (maculopapular, scarlatiniform)
Palpable cervical lymph nodes
Swelling and redness of hands/feet
Irritability is common.
Diagnostic Criteria:
Diagnosis is clinical, based on prolonged fever (>5 days) plus at least four of the five principal clinical features (conjunctivitis, oral changes, rash, extremity changes, cervical lymphadenopathy)
An incomplete form can be diagnosed with fever plus fewer than four features if coronary artery abnormalities are present or other criteria are met.
Diagnostic Approach
History Taking:
Detailed history of fever onset and duration
Presence and progression of all diagnostic criteria
Prior cardiac history or known cardiac anomalies
Family history of vasculitis or autoimmune disease
Recent infections or exposures
Immunization status.
Physical Examination:
Thorough systemic examination focusing on the five principal features
Assessment for peripheral edema or induration, rash characteristics, mucosal changes, conjunctival injection, and lymphadenopathy
Evaluation for signs of cardiac involvement such as murmurs or gallops
Assessment of vital signs and hydration status.
Investigations:
Echocardiography is essential for assessing coronary arteries
initial and follow-up scans are critical
Laboratory tests: Complete blood count (CBC) with differential (leukocytosis, thrombocytosis later), C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) (elevated), liver function tests (LFTs) (mild elevation), urinalysis (sterile pyuria)
Cardiac enzymes and ECG are generally not diagnostic but may be used if myocarditis is suspected.
Differential Diagnosis:
Viral exanthems (measles, adenovirus, enterovirus)
Bacterial infections (scarlet fever, staphylococcal scalded skin syndrome)
Other vasculitides (Henoch-Schönlein purpura)
Stevens-Johnson syndrome
Adenovirus infection
Juvenile idiopathic arthritis.
Management
Initial Management:
Intravenous immunoglobulin (IVIG) 2 g/kg over 10-12 hours
Aspirin: 80-100 mg/kg/day in 4 divided doses until afebrile for 48-72 hours, then reduced to 3-5 mg/kg/day for at least 4-6 weeks (or longer if CAA persists).
Medical Management:
IVIG is the cornerstone therapy for reducing CAA
Aspirin is used for its anti-inflammatory and antithrombotic effects
In high-risk patients or those refractory to IVIG, additional therapies like corticosteroids, infliximab, or cyclosporine may be considered.
Surgical Management:
Surgery is rarely indicated for acute Kawasaki disease
However, patients with giant coronary aneurysms may require surgical intervention (e.g., coronary artery bypass grafting) or interventional cardiology procedures later in life due to long-term sequelae.
Supportive Care:
Fever management with acetaminophen
Adequate hydration
Close monitoring for signs of cardiac compromise or coronary artery aneurysms
Education of parents regarding disease course and follow-up.
Coronary Surveillance Schedule
Initial Assessment:
Echocardiogram within the first week of illness (ideally by day 7) to assess for coronary artery dilation or aneurysms
Criteria for z-score: Normal <2.0
Dilation 2.0-2.49
Mild Aneurysm 2.5-4.9
Moderate Aneurysm 5.0-9.9
Giant Aneurysm ≥10.0.
Low Risk Patients:
Children treated with IVIG within the first 10 days of illness and who have no coronary artery abnormalities on initial echocardiogram
Follow-up echocardiogram at 2-3 weeks
If normal, routine follow-up may be discontinued.
Medium Risk Patients:
Children with coronary artery dilation (z-score 2.0-2.49) or those treated late (>10 days of illness) but with no significant aneurysms
Echocardiograms at 2-3 weeks, 6-8 weeks, and then annually until coronary dimensions normalize
Aspirin 3-5 mg/kg/day should be continued.
High Risk Patients:
Children with coronary artery aneurysms (z-score ≥2.5, especially moderate or giant aneurysms)
Intensive surveillance with frequent echocardiograms (e.g., 1 week, 2-3 weeks, 4-6 weeks, 3 months, 6 months, 12 months, and then annually or biannually based on aneurysm size and stability)
Long-term antiplatelet therapy (e.g., aspirin or warfarin for giant aneurysms) is often required to prevent thrombosis.
Follow Up Goals:
To detect the development or progression of coronary artery abnormalities
To monitor for potential complications such as thrombosis, stenosis, or myocardial infarction
To guide long-term management, including pharmacotherapy and potential interventional or surgical procedures.
Complications
Early Complications:
Myocarditis, pericarditis, valvulitis, heart failure
Coronary artery aneurysms (most significant).
Late Complications:
Coronary artery stenosis, thrombosis, myocardial infarction, sudden cardiac death, arrhythmias, valvular regurgitation.
Prevention Strategies:
Prompt recognition and initiation of IVIG treatment within 10 days of fever onset to minimize CAA risk
Long-term aspirin therapy for patients with coronary abnormalities
Regular echocardiographic surveillance to monitor CAA and guide management.
Prognosis
Factors Affecting Prognosis:
Timeliness of IVIG treatment
Development and severity of coronary artery abnormalities
Presence of residual stenosis or thrombosis
Adherence to follow-up and medical therapy.
Outcomes:
With timely treatment and no significant coronary involvement, prognosis is excellent with resolution of inflammation and normal cardiac function
Patients with coronary aneurysms have an increased risk of long-term cardiovascular events, requiring lifelong monitoring.
Follow Up:
Duration of follow-up depends on the presence and severity of coronary artery abnormalities
Patients with normal coronaries may require only a few follow-up echocardiograms
Those with aneurysms require extended and intensive follow-up, often into adulthood, with careful management of cardiovascular risk factors.
Key Points
Exam Focus:
Recognize KD diagnostic criteria
Understand the role and timing of IVIG and aspirin
Critically important: the surveillance schedule for coronary arteries based on echocardiographic findings (z-scores) and treatment timing
Differentiate between dilation, mild, moderate, and giant aneurysms.
Clinical Pearls:
Suspect incomplete KD in children with prolonged fever and atypical symptoms
Serial echocardiograms are paramount for management decisions
Z-scores, not absolute diameter, are used to define coronary artery abnormalities
Early IVIG is key to preventing aneurysms.
Common Mistakes:
Delaying echocardiography beyond the first week
Inadequate aspirin dosing or duration
Inconsistent follow-up for patients with coronary abnormalities
Misinterpreting coronary artery Z-scores or over-reliance on absolute diameters.