Background: The aim of the present study was to determine the prevalence of coronary artery abnormality (CAA) and other clinical features in patients with incomplete Kawasaki disease (iKD) using the data from the 17th Japanese nationwide survey of KD.
Methods: iKD was defined as the presence of four or fewer of the principal symptoms of the Japanese diagnostic guidelines, regardless of whether the patient had CAA. A total of 15,857 cases were analyzed.
Results: Among 15,857 cases, 83.9% of patients had five to six principal symptoms (complete KD: cKD), and 16.1% had iKD. The prevalence of CAA in cKD was 14.2%, and 18.4% in iKD. The prevalence of CAA in patients with four principal symptoms was 18.1%, which was higher than in cKD cases (14.2%). Although the reliability of the data has some limitations, the prevalence of CAA among patients with one to three symptoms was 19.3%. Among all CAA patients, 14% had four symptoms, and 6% had only one to three symptoms.
Conclusion: Incomplete KD should not be equated with mild KD. Patients with four principal symptoms were comparable to cKD with respect to CAA occurrence. In patients with one to three symptoms also, especially in those under 1 year and older than 4 years of age, other significant symptoms and laboratory findings of the guidelines are very important in making a correct and early diagnosis of iKD so as to prevent CAA.