Most children with Kawasaki disease get better and have no long-term effects, even if they do not receive treatment. However, treatment shortens the illness and greatly reduces the chances of having problems from Kawasaki disease.
About 20% of children who are not treated will have problems in the arteries that supply blood to the heart (coronary artery disease). Weakened coronary arteries may get enlarged or can narrow or develop blood clots. In very rare cases, this can lead to a heart attack.
The risk of heart attack is greatest within 1 year after the illness. However, studies in Japan indicate that children who develop coronary artery damage are more prone to having a heart attack as young adults
