New England Journal of Medicine, Volume 394, Issue 15, Pages 1480–1490, April 16, 2026

A randomized clinical trial published in the New England Journal of Medicine on April 16, 2026, found that adding a short course of prednisolone to standard intravenous immunoglobulin therapy did not significantly reduce the risk of coronary artery abnormalities in children with Kawasaki disease compared to intravenous immunoglobulin alone.

The study, conducted across multiple sites in Japan, enrolled 358 children diagnosed with Kawasaki disease who were randomly assigned to receive either adjunctive oral prednisolone (2 mg/kg per day for three days) or placebo, in addition to standard treatment with intravenous immunoglobulin (2 g/kg) and aspirin. The primary outcome was the development of coronary artery abnormalities, defined as a Z-score of 2.5 or higher, measured by echocardiography at two and four weeks after treatment initiation.

Results showed that coronary artery abnormalities occurred in 12.3% of children in the prednisolone group and 13.7% in the placebo group, a difference that was not statistically significant (relative risk, 0.90; 95% confidence interval, 0.58 to 1.40; P=0.64). There were also no significant differences between the two groups in the incidence of fever persistence or resistance to initial intravenous immunoglobulin treatment.

Adverse events were generally mild and occurred with similar frequency in both groups. Vomiting or regurgitation was reported more frequently in the prednisolone group (18.4%) compared to the placebo group (10.1%), while other side effects such as irritability, hyperglycemia, and elevated liver enzymes showed no meaningful differences between groups.

The researchers concluded that adjunctive prednisolone did not provide additional benefit over standard therapy in reducing coronary artery damage in this population of children with Kawasaki disease. They noted that the findings contrast with some earlier observational studies and smaller trials that had suggested a potential benefit of corticosteroids in certain high-risk subgroups, but emphasized that their large, randomized design provides more reliable evidence regarding the routine use of prednisolone in acute Kawasaki disease treatment.

Kawasaki disease is the most common cause of acquired heart disease in children in developed countries, and while intravenous immunoglobulin remains the standard first-line treatment, approximately 10 to 20 percent of patients do not respond adequately and are at risk for coronary complications. The search for effective adjunctive therapies continues, but this trial indicates that prednisolone, at the dose and duration tested, does not fulfill that role broadly.

The study authors acknowledged limitations, including the exclusion of children with severe or refractory disease at enrollment, which may limit generalizability to the highest-risk patients. They also noted that the three-day prednisolone course was chosen based on prior safety data, and that different dosing regimens or longer durations were not evaluated in this trial.

An accompanying editorial in the same issue of the New England Journal of Medicine highlighted the importance of large, randomized trials in resolving uncertainties about adjunctive therapies for Kawasaki disease, while noting that future research may need to focus on identifying specific patient subgroups who might still benefit from corticosteroid treatment, or on alternative immunomodulatory approaches.