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0.1. Scheme

0.2. Purpose

Conduct randomized controlled trial to test the hypothesis that initial high-dose immunoglobulin plus prednisolone combination therapy is superior to standard high-dose immunoglobulin treatment for patients with severe (risk score, ≥5 points) Kawasaki disease.

0.3. Endpoints

Frequency of coronary lesions occurring during the trial is the primary endpoint. The secondary endpoints are frequency of coronary lesions at 4 weeks after the start of treatment; Z-scores for the main trunks of the right and left coronary arteries and their anterior descending branches; percentage of patients refractory to treatment; number of days from start of treatment to end of fever; CRP levels at 1 and 2 weeks after start of treatment; and frequency of adverse drug reactions. Echocardiographic findings before registration, and at 1, 2, and 4 weeks after start

0.4. Criteria for inclusion and exclusion

1) severe Kawasaki disease (risk score, ≥5 points)
2) accompanied by fever
3) Kawasaki disease diagnosed within 8 days of illness
4) no coronary lesions as a complication before registration (echocardiogram)
5) no past history of Kawasaki disease
6) no disease resembling Kawasaki disease
7) no active, severe, bacterial infection as a complication
8) no steroid use in the previous 28 days either orally, or through intravenous, muscular, or subcutaneous injection
9) no intravenous injection of gamma globulin in the previous 180 days
10) no serious underlying diseases or disorders
11) written consent to participate in this study obtained from either the patient's family or the patient

0.5. Treatment

Group G: High-dose immunoglobulin therapy (IVIG therapy)
* Administer 2 g/kg/day of IVIG via intravenous drip infusion within a 24-hour period.
* As part of initial treatment, administer aspirin (ASA) at a daily dose of 30 mg/kg, given in 3 equal doses.
In general, give ASA even to patients with AST and ALT values that have increased before the start of treatment. The dose may be reduced to 5 mg/kg/day (QD) after a decline of fever has been confirmed, in conformity with the respective hospital's treatment protocol.

Group P: High-dose immunoglobulin therapy plus prednisolone therapy (IVIG + PSL therapy)
* Group G regimen plus intravenous drip infusion of prednisolone (PSL) 2 mg/kg/day as initial treatment.
When administering PSL intravenously, give in 3 equal doses per day for a minimum of 5 days. If fever decreases on day 6 or later of PSL administration, change to oral PSL administration (TID).
* With Day 1 defined as the day when CRP level decreases to <0.5 mg/dL, continue administering PSL 2 mg/kg/day in 3 equal doses through Day 5. Then, taper the dose to 1 mg/kg/day (BID) from Day 6 through 10, to 0.5 mg/kg/day (QD) from Day 11 through Day 15, and then to zero.
* If relapse is suspected, the dose of PSL may be increased again, or the administration period may be extended.
* During PSL administration, give 0.5 mg/kg/day of oral or intravenous famotidine.

The maximum dose of PSL is 60 mg/day. Therefore, if a patient weighs more than 30 kg, reduce the PSL dose as follows: 60 mg/day --> 30 mg/day --> 15 mg/day.

0.6. Planned number of registered patients and research period

Projected number of registered patients: 392
Registration period: 3 years
Follow-up period: 1 month after the end of registration
Duration of trial: 3 years and 1 month