Kawasaki disease

Disease Description (Causes and Symptoms)

• Definition: Kawasaki disease is an acute systemic vasculitis that occurs mainly in infants and young children (most commonly those aged 5 years or younger) and can cause cardiac complications through coronary artery involvement. Seasonality (spring and winter) and epidemic cycles (every 2–4 years) have been observed.
• Causes/Pathophysiology: The exact cause is unknown. A combination of genetic predisposition and an abnormal immune response after exposure to bacteria or viruses (including antibody formation against the vascular endothelium and systemic inflammation) is suspected to be involved.
• Main symptoms: Diagnosis may be possible when fever lasting 5 days or more (or high fever not explained by another cause) is accompanied by 4 or more of the following findings, or by coronary artery abnormalities.
  • Bilateral nonpurulent conjunctival injection
  • Oral and pharyngeal mucosal changes (red lips, fissures, strawberry tongue)
  • Erythema and edema of the hands and feet or desquamation during the recovery phase
  • Rash (various forms)
  • Nonpurulent cervical lymphadenopathy (>1.5 cm)
• Other findings and tests: Diarrhea, vomiting, abdominal pain, elevated liver enzymes (AST/ALT), gallbladder hydrops, leukocytosis and elevated ESR/CRP on blood tests, thrombocytosis after 2–3 weeks, leukocytes in the urine, proteinuria, and others.
• Risk of complications: During the acute phase (approximately after 10 days), complications may include myocarditis, pericardial effusion, arrhythmia, valvular abnormalities, and coronary artery aneurysm (occurring in approximately 20–25% of untreated cases; reduced to approximately 3–5% with IVIG administration).

Treatment Methods and Precautions

• Standard acute-phase treatment
  • Intravenous immunoglobulin (IVIG) 2 g/kg as a single intravenous infusion (administration within 10 days of fever onset is recommended whenever possible) — greatly reduces the incidence of coronary artery complications.
  • Aspirin: Start with a high dose during the acute phase (varying by country and institution; for example, 30–50 mg/kg/day), then switch to a low-dose antiplatelet regimen (for example, 3–5 mg/kg/day) after fever reduction and inflammation control; administer for 6–8 weeks if there are no coronary artery abnormalities.
• Patients with a poor response to IVIG (IVIG resistance)
  • Additional IVIG (readministration), high-dose corticosteroids (especially for high-risk patients or when there is no response to IVIG), TNF-α inhibitors (for example, infliximab), immunosuppressants (for example, cyclosporine), and other options may be considered — according to the individual patient’s condition and the center’s protocol.
• Management of coronary artery abnormalities
  • If a coronary artery aneurysm persists, long-term low-dose aspirin or anticoagulation (for example, warfarin or LMWH) may be considered in combination, depending on the size of the aneurysm and the risk of thrombosis.
  • If stenosis or signs of ischemia are present, treatment such as calcium channel blockers, coronary intervention (PCI), or surgical bypass may be provided at the discretion of a cardiologist.
• Follow-up testing
  • Electrocardiography and echocardiography should be performed in all suspected and confirmed patients, with follow-up at times such as during the acute phase, at 1–2 weeks, and at 6–8 weeks. For moderate or greater coronary artery changes (for example, an elevated Z-score or diameter ≥5 mm), long-term regular follow-up (including echocardiography, exercise stress testing, and nuclear medicine tests) is recommended.
• Precautions (including self-care)
  • Check for allergies and previous use of immunoglobulin before IVIG administration.
  • Monitor the risk of bleeding, gastrointestinal symptoms, and changes in liver enzyme levels during aspirin treatment.
  • Live vaccines (for example, MMR and BCG) may be less effective because of antibody transfer after IVIG administration — follow pediatric guidelines for the vaccination schedule (a delay may be necessary).
  • Seek medical attention immediately if emergency signs such as persistent fever, difficulty breathing, chest pain, or altered consciousness occur.
• Prognosis: With appropriate early treatment, the prognosis is generally good. The recurrence rate is approximately 1–3%, and the mortality rate is very low (less than 0.1% according to available data).

Checklist Before an Outpatient Visit (Including Items to Bring and Example Questions)

• Items to bring
  • A list of currently taken medications and their doses (including aspirin and anticoagulants)
  • Past medical history (especially heart disease, allergies, previous IVIG or blood product administration, and vaccination records)
  • A log of the time recent fever began and changes in symptoms (temperature records; photographs of rash, lips, or conjunctival changes if possible)
  • Copies of previous test results, if available (echocardiography, blood tests, etc.)
• Test and symptom records
  • Number of days with fever, response to antipyretics, urine output, changes in appetite and fluid intake, and the presence or absence of respiratory or gastrointestinal symptoms
• Important information to report at the outpatient visit
  • Drug allergies (especially aspirin), bleeding tendency, and family history (cardiovascular disease, abnormal bleeding, etc.)

Examples of General Questions to Ask the Doctor

• What are the main side effects of this treatment (IVIG and aspirin)? What monitoring items should we expect?
• What is our child’s risk of coronary artery involvement (or what is the current condition of the coronary arteries)? How often should echocardiography be performed?
• How long should aspirin be taken, and what lifestyle precautions should be followed during outpatient visits while taking it?
• When can future vaccinations (especially live vaccines) be resumed?
• If the disease recurs or treatment fails, what additional treatments might be needed?

Examples of Disease-Specific Questions

• What is our child’s coronary artery Z-score (or diameter) on echocardiography, and how will the treatment and follow-up plan change according to this value?
• If fever or inflammatory markers do not improve after IVIG administration, what is the next recommended treatment (repeat IVIG, steroids, infliximab, etc.), and what are the expected effects and side effects?