Background: Kawasaki Disease (KD) is associated with coronary artery aneurysms about 20% of untreated children. Treatment with IVIG within the first 10 days of illness reduces the prevalence of coronary artery aneurysms around fivefold. Data of delayed diagnosis of KD in Thailand had been rarely reported.

Objective: To determine the prevalence, clinical manifestations and outcome of delayed diagnosis of KD in Thai patients.
Method: Retrospectively reviewed medical record of the patients diagnosed with KD during 2000-2008 at Chiang-Mai University hospital. Patients were classified in to two groups. Group I : patients diagnosed = 10 days of fever, Group II: patients diagnosed > 10 days of fever.

Result: Twenty of 170 children (11.7%) were in Group II (mean fever 15 ±4 days) and
150 patients were in Group I (mean fever 7 ± 1.45 days). There were no statistical differences between two groups according to age, gender, number of KD clinical manifestations or laboratory results except for lower body weight(p=0.01)in group II. Patients in group II seemed to have younger age (p=0.09) and more incomplete criteria (p=0.09) but there were no statistically significant. The delayed diagnosis group also had higher incidence of coronary artery abnormalities (CAA) (75% versus 19% ) (p<0.001), more severe CAA, more resistance cases (p=.03).

Conclusion: Patients with delayed diagnosis of KD were associated with higher risk of developing CAA and more severe coronary outcome. More education is needed for healthcare providers and physicians to aware of KD especially in small children or incomplete KD.