Characteristics and trends in diagnosis of Kawasaki disease outside the usual age range

OBJECTIVE To explore the trends in diagnosis of Kawasaki disease (KD) and determine the characteristics for patients outside the usual age range of 6 months to 4 years. METHOD A retrospective review of patients with KD identified in four epidemiological surveys spanning 20 years (1998-2017) in Shanghai was performed. RESULTS A total of 8416 patients were included. All in all, 223 (2.6%) were aged 0 to 2 months, 639 (7.6%) were 3 to 5 months, 6556 (77.9%) were 6 months to 4 years, 915 (10.9%) were 5 to 9 years, and 83 (1.0%) were ≥ 10 years. The use of intravenous immunoglobulin increased in all extreme age groups, and delayed treatment rates decreased in all patients except in those aged 0 to 2 months and ≥ 10 years. The number of patients outside the usual age increased over time, but the proportion of these patients did not change significantly. They had more incomplete KD and coronary artery aneurysms (CAA), while those aged 0 to 2 months and ≥ 10 years had more delayed diagnoses in their respective age groups. The incidence of CAA was similar in younger and older children, but the former group had more cases of incomplete KD and abnormal laboratory parameters, while the latter group had longer duration of fever and was more difficult to diagnose promptly. CONCLUSIONS The proportion of KD outside the usual age range did not increase over time. Older and younger children have different clinical and laboratory characteristics. Key Points • The number of patients outside the usual age increased over time, but the proportion of these patients did not increase. • Patients aged 0 to 2 months and ≥ 10 years had more delayed diagnoses in their respective age groups. • Younger children had more cases of incomplete KD and abnormal laboratory parameters, while older children had longer duration of fever and were more difficult to diagnose promptly.