Treatment change and coronary artery abnormality in incomplete Kawasaki disease.

Background Incomplete Kawasaki disease (iKD) showed a higher incidence of coronary artery abnormalities (CAAs) than complete KD. However, the incidence of CAAs among iKD patients may have changed recently. Methods We examined KD patients from recent nationwide surveys conducted between 2013 and 2016 and compared them with the results of a previous survey (2001-2002). Results Of 63 270 KD patients, 13 770 patients (22%) had iKD. They showed a higher incidence of convalescent-phase CAAs (cCAAs, 2.8%) than complete KD (2.1%). The incidence of cCAAs in patients with one or two symptoms (6.7%) was significantly higher than those with three or four symptoms (2.6%) (P< 0.0001). Intravenous immunoglobulin (IVIG) treatment was administered to 80% of iKD patients; 30% of them received IVIG before the fifth illness day (early treatment) and 12% of patients received IVIG after the seventh illness day (late treatment). In the previous survey, the incidence of cCAAs was higher in both iKD (5.9%) and cKD (4.4%). Intravenous immunoglobulin was administered to 62% of iKD patients; 26% of them received early treatment, and 16% received late treatment. Conclusions The incidence of cCAAs remained higher among iKD patients than cKD patients but this difference was reduced by the increased proportion of iKD patients treated with IVIG and those at an earlier time point. It is important to recognize the possibility that patients may have iKD and perform echocardiography even if they present with a few principal symptoms.