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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Kawasaki disease = fever >=5 days plus mucocutaneous findings: conjunctivitis, oral changes, extremity changes, rash, and cervical lymphadenopathy
- It is the leading cause of acquired heart disease in children in the United States
- Most important complication is coronary artery aneurysm; obtain echocardiography at diagnosis and follow-up
- Treat within 10 days with IVIG plus aspirin to reduce coronary aneurysm risk
- Incomplete Kawasaki disease is common in infants and should be considered with prolonged unexplained fever and elevated inflammatory markers
Overview
Kawasaki disease is an acute self-limited vasculitis that predominantly affects medium-sized arteries, especially coronary arteries. Diagnosis is clinical and should not be delayed while waiting for a confirmatory test. The classic criteria are prolonged fever plus four of five principal features, but incomplete Kawasaki disease is important in infants and can still cause coronary complications. USMLE questions often compare Kawasaki disease with scarlet fever, measles, adenovirus, toxic shock syndrome, and MIS-C.
Epidemiology
Kawasaki disease most often affects children younger than 5 years, with highest incidence in children of East Asian ancestry but cases occur across all groups. Coronary artery aneurysms develop in a substantial proportion of untreated children and are dramatically reduced by timely IVIG. Seasonal clustering and infectious triggers are suspected, but no single cause has been confirmed.
Clinical Features
Symptoms
Fever for at least 5 days, often high and unresponsive to antipyretics
Irritability, poor intake, abdominal pain, vomiting, or diarrhea
Red eyes without purulent discharge
Painful swollen hands/feet or later periungual peeling
Chest pain, dyspnea, syncope, or shock are concerning for cardiac involvement or MIS-C mimic
Signs
Bilateral nonexudative conjunctival injection
Oral mucosal changes: cracked red lips, strawberry tongue, diffuse oropharyngeal erythema without exudate
Polymorphous rash, often truncal; not vesicular
Extremity erythema/edema acutely; periungual desquamation in subacute phase
Cervical lymphadenopathy, classically unilateral node >1.5 cm
Murmur, gallop, hepatomegaly, or signs of myocarditis/shock
Investigations
First-line
Clinical diagnostic criteriaFever >=5 days plus >=4 principal features; incomplete disease uses labs and echo when criteria are not fully met
Inflammatory markersElevated CRP/ESR supports diagnosis; thrombocytosis often appears after day 7
CBC, CMP, urinalysisAnemia, leukocytosis, thrombocytosis, elevated ALT, hypoalbuminemia, sterile pyuria support diagnosis
EchocardiogramEvaluate coronary artery dilation/aneurysm, myocarditis, valvular regurgitation, and pericardial effusion
Second-line
ECG and troponin/BNPIf myocarditis, arrhythmia, or shock is suspected
Infectious testingTargeted testing for adenovirus, measles, strep, COVID/MIS-C, or toxic shock when clinically indicated
Repeat echocardiographyTypically at diagnosis and follow-up intervals; more frequent if coronary abnormalities are present
Specialist
Pediatric cardiologyAll suspected Kawasaki disease requires echocardiography and cardiology follow-up
Rheumatology/infectious diseasesIVIG-resistant, incomplete, recurrent, or diagnostically uncertain cases
1
Initial treatment
- IVIG 2 g/kg single infusion, ideally within first 10 days of illness; treat later if ongoing fever/inflammation or coronary abnormalities
- Aspirin is used acutely; dosing strategy varies, but transition to low-dose antiplatelet therapy after fever resolves
- Baseline echocardiogram should be obtained but treatment should not be delayed if echo is not immediately available
2
Incomplete Kawasaki disease
- Consider in infants <6 months with fever >=7 days and inflammation even if few classic signs
- Use CRP/ESR and supplemental labs such as anemia, thrombocytosis after day 7, hypoalbuminemia, elevated ALT, leukocytosis, and sterile pyuria
- Abnormal echocardiogram or supportive labs should prompt IVIG treatment
3
IVIG-resistant disease
- Persistent or recrudescent fever at least 36 hours after IVIG completion suggests IVIG resistance
- Options include second IVIG, corticosteroids, infliximab, or other immunomodulatory therapy in specialist pathways
- High-risk patients may receive adjunctive corticosteroids depending risk stratification and local practice
4
Long-term cardiac management
- Low-dose aspirin continues until no coronary changes are present on follow-up; longer antithrombotic therapy for aneurysms
- Avoid live vaccines for a period after IVIG because passive antibodies may reduce vaccine response
- Coronary aneurysms require cardiology-directed thrombosis prevention, activity guidance, and long-term surveillance
Complications
- Coronary artery aneurysm: Most important complication; may cause thrombosis, stenosis, myocardial infarction, or sudden death
- Myocarditis: Can cause depressed ventricular function, shock, or arrhythmia
- Valvular regurgitation: Mitral regurgitation can occur during acute inflammation
- Macrophage activation or shock-like presentations: Severe systemic inflammation may mimic toxic shock or MIS-C
- Aspirin adverse effects: Bleeding and Reye syndrome concern; influenza and varicella exposure need careful management
USMLE Step 2 CK Exam Tips
- 1Fever >=5 days + conjunctivitis + mucosal changes + rash + extremity changes + cervical node = Kawasaki disease
- 2Most feared complication is coronary artery aneurysm, not the rash
- 3Treat with IVIG plus aspirin within 10 days; do not wait for coronary aneurysm to appear
- 4Bilateral nonpurulent conjunctivitis helps distinguish Kawasaki from bacterial conjunctivitis
- 5Incomplete Kawasaki is especially important in infants with prolonged unexplained fever
- 6Thrombocytosis is classically a subacute finding after the first week
- 7Avoid live vaccines after IVIG for the recommended interval because vaccine response may be blunted
- 8Kawasaki has oral erythema/strawberry tongue but no exudative pharyngitis
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