Background: Kawasaki disease (KD) remains a diagnostic challenge due to its nonspecific clinical symptoms. Delayed treatment initiation increases the risk of coronary complications.

Aim: To evaluate the risk of coronary artery involvement and perform a prospective analysis of its course in children hospitaliseddue to KD.

Methods: KD was diagnosed in 38 children, including 25 boys and 13 girls, aged 1.5–118 months (median 37.5 months). We assessed the risk of cardiac complications in relation to the presence of a complete or incomplete form of the disease, age, gender and laboratory test results, as well as the timing of treatment initiation. Thirty-six children were followed for 1–9 yearsin a cardiology clinic.

Results: More than 80% of patients with KD were younger than 5 years. Eleven (29%) of them had an incomplete form of the disease. Coronary artery abnormalities were found in 10 (26%) children, insignificantly more often among those within complete KD. Each day of treatment delay increased the complication rate by almost 1.5 (OR 1.45, p = 0.009). Treatment initiated 10 days after the onset of the disease increased this risk almost nine times (OR 8.99, p = 0.007). No significant differences in respect to age (p = 0.431), gender (p = 0.744) and laboratory test results were found between the groups with and without coronary complications. A complete regression of coronary artery involvement was seen in 7 children, and partial regression was seen in one child. One child died and another needed coronary artery bypass grafting.

Conclusions: Coronary artery aneurysms developed at a similar rate in both complete and incomplete forms of KD and the only significant risk factor was the timing of treatment initiation. In young children with fever of unknown cause lasting longer than 5 days, echocardiography is warranted. Despite a tendency for coronary artery aneurysms to regress, late complications may occur and all children require long-term follow up in a cardiology clinic.