Changes in Kawasaki disease incidence and phenotype during the COVID-19 pandemic

INTRODUCTION. The aetiology of Kawasaki disease (KD) remains unknown. Changes in infectious exposure during the COVID-19 pandemic owing to infection prevention measures may have affected the incidence of KD, supporting the pathogenic role of an infectious trigger. The purpose of this study was to evaluate the incidence, phenotype and outcome of KD before and during the COVID-19 pandemic in Denmark. METHODS. This was a retrospective cohort study based on patients diagnosed with KD at a Danish paediatric tertiary referral centre from 1 January 2008 to 1 September 2021. RESULTS. A total of 74 patients met the KD criteria of whom ten were observed during the COVID-19 pandemic in Denmark. All of these patients were negative for SARS-CoV- 2 DNA and antibodies. A high KD incidence was observed during the first six months of the pandemic, but no patients were diagnosed during the following 12 months. Clinical KD criteria were equally met in both groups. The fraction of intravenous immunoglobulin ( IVIG) non-responders was higher in the pandemic group (60%) than in the in the pre-pandemic group (28.3%), although the rate of timely administered IVIG treatment was the same in both groups (>= 80%). Coronary artery dilation was observed in 21.9% in the pre-pandemic group compared with 0% in KD patients diagnosed during the pandemic. CONCLUSION. Changes in KD incidence and phenotype were seen during the COVID-19 pandemic. Patients diagnosed with KD during the pandemic had complete KD, higher liver transaminases and significant IVIG resistance but no coronary artery involvement.